US2010422A - Excavation means - Google Patents

Description

Allg. 6, 1935- w. F. TowNsEND EXWYATION MEANS Filed May 19, 1930 INVENTOR Patented Aug. 6, 1935 UNITED STATES PATENT OFFICE y l 2,010,422 I p ExcAvATloNiuEANs l y William F. Townsend, Flushing,` N. Y. Application May 19, 1930, serial No; 453,831

' s claims. (ci. ce1-85)'` n Y Y `adapted to be readily verected and knocked down This invention relates to excavation means, and more particularly to excavation means used to drive shafts or tunnels, such as tunnel shields.

One of the objects'of my invention is during `5 the excavating operation to compress the 'material radially outwardly by Wedging-means or specially arranged cutting means around the mouth of the excavating 4device and then to release said material by the progression ofthe excavating device and thereby automatically lallow it to expand into full surrounding support against the outside of the tunnel lor shaft-lining vpreviously erected in the rear end of the excavatingdevice and from which it emerges during said releasing progression of the device.

Another object is to excavate soft ground automatically by forcing it through openings provided for the purpose in the header -of the excavating device as it is forced against said material, said material being delivered through pipes or'chutes inconnection with said header openings Vto conveyances for removing and disposing of it.

Another object is to specially irrigate the material in advance of the excavating device to make said material work like soft ground in connection with my invention` Another object is to provide improved means for forcing ahead the excavation device away from the last erected section of the tunnel-lining, said means comprising jacks having special shoes, whereby the jacks can tilt with reference tothe tunnel-lining, as required by any swerving of the `excavating device, but the shoes will remain squarely seated against the end section of the tunnel-lining and thereby continue to distribute the thrusts evenly over said lining as distinguished from concentrating the thrusts unevenly to the probable damage of the lining.

Another object it to provide in connection with the excavation 'deviceA achute for receiving the excavated material received into the excavating device and deliveringit by gravity but withsa'ie momentum and impact to the conveying means for conveying the material Iout of the excavating device. l v

Another object is to provide an iron or steel bulk-head construction with its air-locks in lieu of the bulk-heads., now in use, my iron or steel'bulkhead being devised so as to be adapted to be anchored to the lining of the excavation so effectively and over such a Wide arcaof the liningthat it presents far greater resistance to the high air pressures involv-ed'than has been attainedhere- `tofore, and is therefore farV safer than the present steel construction; and which is nmoreover in portable units and as such, moved along to sucl'cessive locations and reassembled.

Another object is to make `tunneling and the `sinking of shafts more rapid, lesscostly and mfproved in result.

Other objects will be in part-apparent to those skilled in the art or in part pointed out hereinafter.

Theinvention accordingly consists in the features of constructionfand mode of operation, combination ofelements and arrangementsof parts asA willbe exemplified in the method and structure 4to be hereinafter described; and' the scope of the application of which ywillbe indicated in the following claims.

i In order that the. invention may be readily un- Iderstood and its advantages from a practical .standpoint fully appreciated, reference may be .had to the accompanying drawing showing one of the preferred forms of embodiment which my .present invention is adapted to take.

In `the drawing, Fig. 1 is a vertical longitudinal section partly in elevation oi Aa tunnel-heading on the line I-I in Fig.!2 and shows a shield, a

ltunnel-lining and arlbulk-head enclosing a compressed air .chamberLbetween them, these embodying preferred forms of parts and structures withinxmy invention; Fig; 1a is an enlarged de- .tail of the manner in which the rings of tunnel arrows; Fig. 5 is aview on'V the line 5-5 in Fig. 4 Ashowing the base of the socket-part of the push- Ving-shoe; Fig. 6 is an enlarged elevation of that part of the pushing-shoewhichis at .the end of the tunnel-liningpFigrl is anfenlarged 1ongirtudinal. section through the circular girder of the .bulk-head containing the air-locks and. through .the .tunnel-lining' and the concrete connection :between said girder and lining; Fig.` 8 corresponds to Fig. 4 except that itshoWsa vmodified form of pushing-shoe of a jack which omits the ball and -socketconstruction shown in Fig. 4; Ienlarged section of. the mannerin `which the Fig. 49 is an irrigating pipes of my invention may'beconstructed. Fig. 10 is an elevation partly in section of a gate or valve device capable of contributing toward the control of the course of the shield of the present invention.

In the drawing the invention is shown as applied to a device for driving tunnels as distinguished from a caisson for sinking shafts. However, many, if not all, of my herein improvements apply equally Well to excavating devices generally, whether for driving tunnels or .sinking shafts; and this is to be understood or implied in connection with the following detaileddescription and the claims.

In the drawing, the tunnel excavating device or so-called shield, generally designated bythe letter A, comprises a tubularshell J4, a bulkhead or header 23 preferably supported within and carried by said shell, and cuttingmeans I at` the mouth of the forward end of thenshell.

The shield A; the air-lock bulkhead,`generally designated B; and the tunnel-lining generally designated C enclosebetween them the space D which is the compressedair chamber in which rthe men work to carry on thetunneling operation, the compressed air, of course, serving to keep the water out of the working space aswell as to supply the men with air to breathe.

Jacks, generally designated E, serve to force the shield endwise towards the right in Fig.; l

into the ground or material to be excavated which is either excavated, by hand or is automatically delivered intoV the shell in accordance with my invention, and thence delivered through the locks 1in the bulkfhead B for nal -disposal Vthereof.

The space in the shell of the excavating shield behind its header forms part of4 the compressed air working space and vpermits the men to erect the successive rings H of the tunnel-lining C within the tail end of the shield as the latter is pushed forward and the materialis excavated tdform thetunnel.

These jacks extend lengthwise of the shell in a circumferential series around the interior thereof; and they doperate between the end of the last erected` ring of the tunnel-lining C and the header f23 ofthe shield, or more specifically the ringshaped` girder 25 to whichthe shell l!! and the peripheralportion of saidheader 23 are secured.

`Fig. 1 shows the last rings ll lof the tunnel-lining that have been erected within the tail end of the tshell against which thejack-shoes bear as aforesaid to force .the shieldA forwardinto the lmaterial to be excavated. Fig. la shows in vdetail the manner in'` which these rings'may be placed placed by the outer cross-section of the shell i4 and of compressing the remaining material radially outwardly and holding it'in compression by the outsideof the shell i4 as the latter is'advanced by the jacks through Ythe material. This compression is only released when-the tail-end of the shell has passed beyond; it, whereupon the .eompressed'material expands inwardly into contact with the outsideY of the tunnel-lining sections or rings Il as they emerge from the tail- .end of the shell due toits advance into the material. 1 l.. i ,j

It will be understood that the aforesaid metallic cutting edge l completely surrounds the perimeter or mouth of the shield and the front or bottom of a caisson. For convenience of application, removal and replacement, this cutting edge is usually made up in sections secured end to end an and to the skin or shell or other frame work of the shield or caisson.

The openings il are provided through the header 23 of the shield or other excavating device from which preferably chutes, designated ila, lead rearwardly into the shell.' rlhe material .from in front of the header is automatically nforced through these openings and chutes by the operation of forcing the shield and header against the material bymeans of the jacks. Thus, the openings 'il and chutes ila form part of an efficient means for automatically excavating the soft material in front of the header and for automatically delivering it into conveyances at the shield such as cars, conveyors, etc., for subsequent removal.

The foregoing assumes that the ground ahead of the shield or the like is suiiiclently soft and .plastic for the purpose. If not, irrigation means .is provided comprising the pipes i8 adapted to be projected through suitably provided holes in the header into the material in front of it in order to deliver water or liquid under pressure from .any suitable source of supply into said material to soften it so that the material will be sufi'lciently soft to squeeze or ow through the aforesaid `openings il during the advance of the shield. Similarly, in such case, pipes it@ are'provided for irrigating the material at the periphery of ther shield, these being adapted to be projected rinto said material through holes provided for the purpose in the shell or skin of the shield.

. The holes Vin the pipes for delivering this liquid yconsist of a large number of fine holes i313 through vthewalls of the pipes for the distance the pipes enter the ground; whereas the end of each pipe is lplugged up or closed. Moreover, said holes in the walls are -countersunk slightly at the outside of the walls Vto prevent them from being plugged when pushing or projecting them into the ground as heretofore described. This construction is Yclearly indicated in Fig. 9 which also shows a simple manner in which the pipes may be housed for reciprocating movement through the header 23.

On the other hand, I do not limit myself to impregnating the ground with liquid by pipes projected or forced ahead of the shield bulk-head 23 because in some grounds, such as sand, the

pipes may eind at the bulk-head or header and the water may be simply forced through the ends of pipes directly into the ground in front of said bulk-head.

This irrigation operation takes place while the shield is at rest to prevent damage to the last named radially projecting pipes i5@ which should be withdrawn before the shield is set in motion. On the other hand, it is not necessary to withn draw the irrigation pipes i8 that project through the header, because the advancing shield will automatically bring these back into the shell without damage thereto.

Platforms 2t are supported by the circular or ring-shaped girders of the shield behind the header 23. Vertical chutes l5 for the excavated material are supported in the shell behind the header ,by these platforms and have openings -into theml at said platforms whereby the excavated material coming through the openings Il andchutes lla may be delivered eitherlzdirectly into the aforesaid vertical chutes l5 or` .onto the platforms,` whence it 4canbe shovelled into .the openings of thechutes l5. .An important novelty of the. chutes I5 is their Zig-zag1 form whereby the flow of the material down the chutes is impeded at each elbow therein .with the result that it is dellveredat low velocityto the canor-rne'- chanical conveyor I6 without damaging the latter which cannot be done where the material: is delivered from an upperplatform of a largietunneling shield unless the chute be made extralng so as to be inclined at a small angle,` in which event it ytakes up too much room and involves the further `disadvantages hereinafter more particularly pointed out. For the same purpose of retarding the drop of the material, ribs hereinafter more .particularly described may be provided on`-`the interior of the chutes tofurther reduce the impact of the material upon the conveyor or car.

Gates or valves I'lb, for instance, as shown in Fig. l0, are provided in connection with each opening ll and chute llEL whereby the opening and closing of these vopenings can be controlled selectively. If the shield in the given operation has begun to swerve out of its true course, this can be corrected by appropriately closing some of the openings at one side of the shield and opening some on the other side; or the shield can be deliberately made to swerve with the `object of forming a bend in the tunnel `byselec.- tively manipulating said closures for the openings Il or chutes Ila. i

The heretofore referred to jacks E embody pushing-shoes within my invention whereby said pushing-shoes of the jacks always remain in full or square contact with the adjacent tunnel ring instead of being tilted'out of square contact when the shield swerves. Two forms of these pushingshoes are shown in Figs. 4 and 8 respectively, the former embodying substantially a ball and socket joint. D The jacks E are supported all around the inside of the shield in the channels of the ring-like girders and 25a of vthe shield. Each extends through a hole in the web of the girder 25a and pushes against the web of the girder 25.

Describing first the ball and socket form shown in Figs. 1,4, 5 and 6, each of these pushing-'shoes comprisesA an arcuate plate 3 shown in plan in Fig. 6 adapted to bear against the end of the last tunnel-lining ring I I. Each'of these plates has a boss 3a, shaped in the form of the exterior surface of a portion of a sphere and acting asthe ball part of the joint. The socket part consists of a concave boss 2a shaped in the form of the interior surface of a portion of a sphere, disposed upon another plate 2 and forming a seat to receive and coact with the partially spherical boss 3a. These plates 2 and 3 with their coacting ball and socket portions comprise what I have conveniently called the pushing-shoe and are yieldingly held together and, at the same time, attached to and supported by the base 8 of the related `jack by bolts 4. rIhese bolts projectfreely through suit,- ably located holes in the plate 3 with their heads counter-sunk in the back ofthe plate andwith their Shanks passing freely through enlarged holes in the plate 2 and the base 8 of the jack. The free ends of these bolts beyond the base 8, are provided with spiral springs 5 held thereon by washers 6 and nuts l, the latter engaging the screw-threaded free endsvof -the bolts. l In other words, the circular"girders `25`and 2%l of the shield,` operatively support the'"jacks`iand.

theseinf-'turn :support the ball and socket shoes with `theirarcuate plates 3 at the end of the last tunnelilringllorother form of tunnel-lining; and it will be.4 understood that the arcuate plates 3 `oflall .the jacks form an end-to-end series, so

thatlithey collective thrust of the jacks is distributedpractically over the entire end of the tunnelring including -its'outer peripheral portion. Moreover, these arcuate plates 3lof the shoes always remain squarely seated against the endsection' of the tunnel-'lining in spite of any swervingvertically or laterally of -the shield `as it is pushed forward. When this happens, the combined jack and shoe construction accommodates for-the swer'ving .by permitting the jacks to tilt out of line with-the shoes but without taking the latter 4out of square, full-face contact with the end-section of the tunnel-lining.

1The other form of less expensive pushing-shoe shown' in Fig. `8, `may be used for the sake of economy with jacks pushing against wooden lining or breasting and Working against comparatively l'ight loads. The pushing-shoe of `said Fig. 8 is made ofa heavy structural steel section such as an H-beam `2l)` with its plate stiffeners 2l. In this form of the pushing-shoe, I omit the ball and socket joint,but use the previously described bolts 4, springs 5 and fastenings 6 and 1 as in Fig. 4 to connect the H-beam with the bases of the jacks. When the jack using the pushingshoe of Fig. 8 is called upon to yield laterally, the base 8 of the jack can tilt relatively to the pushing-shoe due to the yielding of the springs 5, but the pushing-shoe itself will still bear squarely against the tunnel ringv as in the other form of pushing-shoe construction.

" These pushing-shoes of my present invention avoid the damage often done by the ordinary jacks to the tunnel-lining arising from the swerving of the shield which causes the. ordinary jacks not provided with myApushing-shoes to tilt and thereby no longer bear squarely against the tunnel-lining end-section over an area equal to the entire base of the jacks. On the contrary, the reaction from the ordinary jacks is often con-A centrated `under these circumstances on a small area of the tunnel-lining and is the common cause of cracked and broken sections of tunnellining sol frequently met with and which must be removed and replaced, resulting in increased cost. All of this is avoided by equipping the jacks with my pushing-shoes.

` When the material tov be excavated is of the nature of pebbles and requires breasting and excavation by hand, I use jacks equipped with pushing-shoes ofl either kind located in the hollow platforms 24 of the shield so as to project forwardly from the interior of said platforms with their pushing-shoes bearing against a timber bulk-head I9, so as to operate it in the usual manner in excavating practice where timber bulkheads or breasting are used.

Instead of employing the usual bulk-head ordinarilybuilt of concrete and some times of steel to form the rear end of the compressed air chamber D,-I provide an improved construction forthis bulk-head of the metal or steel type, my object being to make this bulk-head safe from break- 'downand blow-outs when in use and at the same time 1vmake it easier to assemble and reassemble this bulk-head as called for by the progression of dthe tunnel. 'fMy steel bulk-head construction B comprises a strong tubular shell or web!) secured to and surrounded by a plurality of circularor ring-like structural members le Vhaving annular outwardly directed flangesV lila. Theseanges .Illa` vproject toward the tunnel-lining and are imbedded as shown in concrete which is suitably applied in any well known manner between the rtunnel-lining and the outsideof the shell 9 of the bulk-head S0 as to form a concrete joint extending all around the periphery of the bulk-head between it and the tunnel-lining for the entire length or depth of the bulk-head, which may have any desired length such as that shown whichis equal to two or more widths of the tunnel-liningrings Il.y Preferably, wherever the conditions permit, the outside dia eter of the bulk-headshell 9, conformsclosely to the interior of the tunnel-lining so that the outwardly directed flanges li!2L project into the channels of the tunnel rings il between their flanges and are there imbedded Vin the concrete contained in said channels. This inter-leaving of the anges Illa with the flanges of the tunnel-,rings gives increased strength and-resistance against blow-outs to the concrete union between the bulkhead and the tunnel-lining. In either event, my bulk-head construction has great strength and resistance against displacement applied over a large area of lthe tunnel-lining making it essentially adequate to cope with the great pressures amounting at times to 45 pounds to the square inch upon the bulk-head.

The header l2 of my bulk-head is also preferably made of steel construction properly supported by the aforesaid members 9 and I0 and is equipped with. the air locks I3. 'Ihe structural steel framing for supporting this bulk-head l2 from theparts Si and l0 are omitted from the drawing for the sake of simplicity, since these are engineering details which will vary with the particular size and construction of the given bulkhead. Y

. In any event, the structural members Sl and le, the header I2,and the inter-connecting parts of the bulk-head B in practice will be madevup in sections adapted to be readily assembled and whenever necessary knocked down and reassembled to enable the positionof this bulk-head to be changed and advanced with the progress of the shield. The tunnel-lining C in the particular form illustrated consists of a series of ring-shaped girders Il, circular in this particular instance to correspond to the shell ofthe excavating device which in this case happens tobe cylindrical to excavate a cylindrical tunnel. These ring-like girders are vsecured together side by side and each consists of an annularly vhanged plate with its anges directed radially inwardly. The channel space in each girder is adapted to be lled with concrete.

In the event that other forms of tunnel-lining are used such as a lining made up of concrete blocks or a monolithic lining be used, I still anchor my steel bulk-head B to the tunnel-lining by the concrete joint as heretofore described by keying said concrete joint on the outside with suitably provided recesses in the concrete blocks or monolithic tunnel-lining; and 'by keying it on the inside withy the ilanges Ill:t of my bulk-head construction B. l

I will now amplify the foregoing kdescription with additional comments and details as followsz-In previous excavating practice, the bevelled or sloping face of the cuttingedge Ywas located toward the longitudinal Vaxis or interior of the shell, whereas, I have inverted the construction so that its bevelledor sloping face is directed towardsthe outside of the shell. x By my ama-422 inverted cuttingA edges, `l, Icut and take into the shield, as :it is forced forward by the jacks, a smaller amount of material or ground than the displacement of the shield requires. This difference in quantity of Aintake of material, although lrelatively small compared to the displacement of the shield, is nevertheless import-ant in the oper- -ation ofl my shield or excavating device with its inverted cutting edge.

'Ihe aforesaid material forced radially outwardly by the inverted cutting edge is compressed againstthe ground or material immediately about it, which latter is also compressed, whereby the moisture is forced from it farther into the surrounding ground as the material is compressed to the line of the outside of the shell or skin I4 of the shield. This compression is maintained as long as the advancing shell is in contact with it, but is released as soonas the tail of the shell passes by, whereupon the compressed material expands radially inwardly both because of its release from compression and because it can now reabsorb its quota of moisture from the surrounding ground, the result being that it automatically lls up the void left at the tail of the shell and is forced into supporting Contact all around with the peripheral surface of the adjacent portion of the tunnel-lining.

Previous methods which do not employ my inverted cutting device required the space left by the thickness of the shell to be filled by a special oper-ation consisting in forcing grout, sand or gravel into this space by means of compressed air applied through holes in the tunnel-lining.

Thus, my inverted cutting edge when used in soft ground eliminates these previ-ous methods and their cost which is considerable and not always effective in filling the voids about the tunnel-lining which, if allowed to remain, result in settlement of the ground at the surface and of any constructions in or supported by said ground.

The use of my inverted cutting edge is also applicable advantageously in connection with caissons for sinking shafts in soft ground.

By soft ground I mean to include ground that contains or is saturated with a liquid, or ground that can be moved or compressed by external force applied, for example, by jacks; or ground that is plastic, such as clay, silt, sand, or mixed sand and pebbles, or loam, with a greater or less degree of moisture content.

My inverted cutting edge is made of such a slope,ior may be stepped similarly to a flight of flat stairs, to force outwardly and prevent entrance into the mouth of the shell of the shield, a quantity of material sufficient to ll the void left behind the shield at .the outside of the tunnellining. I do not limit myself to any particular slope or projection of the cutting edge or to any particular material of which it is made, as these matters are capable of wide variation.

Referring to the pipes or chutes Ila, these direct the soft ground delivered sausage-like thereby from the front of the header in any desired or suitable direction to the cars, conveyors or buckets in the shield behind the header, thereby saving the labor cost of handling this material at this point. This saves the great cost of excavating by previous methods of digging, breasting, cutting and loading cars with the excavated material all by hand labor.

V`I do not limit myself to the number, size or position of the chutes I la or openings Il' through the header or of the irrigating pipes I8.

f In practice, I provide Suitable means for conclosing the space.

filled and the concrete or grout has set, the vam' nular flanges of the chord angles and of the bear trolling each opening through the header 23 or. the delivery end of each chute Ha; and this means may consist ofany -suitableform 'of gate or valve, for instance, such as that `indicated. inr Fig. l0. By selectively operating these gates for the different openings H, it becomes possible to make the shield offer greater resistance to ad# Vance at one part thereof than at other parts and thereby makes it possible to directtheprogress of the shield as to line and grade; i

In connection with my improvedfbulk-head B', attempt has been made heretofore to make a steel bulk-head wherein, however, the steelsupports of the face or header of the bulk-head were connected directly at isolatedpoints to the tunnellining and. had the effect of; concentrating the very heavy air pressures on the bulk-headrsay up to lbs. per square inch, upenisolated .parts of the tunnel-lining, which not infrequently causedthe tunnel-lining to break-down and the bulkhead to give Way with resulting loss in life and property. t i

Itis the structural steel beam and channel supports of the header of `the bulk-*head which developed these heavy concentrated loads at their ends and it is where these ends werelconnected directly to the tunnel-lining that the failures occur. Also it is here that I depart fromethe. previous practice by connecting thel structural members carrying the heavy concentrated'reac-l tions of and from the header not directly to the tunnel-lining but to the tubular or web member 9 and the surrounding circular flanges. 1D

, and 'ma of the bulk-head andthence tothe tunnel-lining through the heretofore described in' termediate concrete-joint.connection. 1 In order to formrthis concrete-joint, I assem ble my steel bulk-head in the tunnel out of its component parts and 'then build forms` around the ends of the space between the bulkhead and` the tunnel-lining; I then force by compressed air concrete or grout into said enclosed space through holes in the tubular` member `9, Yof the bulk-head and throughy holes in theformsen-W `When the space is entirely ing angles are embedded inthe concretefthat is now between the outer, peripheral surface of the bulk-head and the inside of the tunnel-lining; and

I thereby obtain support along the entire perimeter of each angle ring and-the flanges of the beams or channels when theyare used insteadof the structural members 9 andfl in connection i with the bulk-head construction. The concrete or grout in turn transmits the load to the tunnel lining over every inch of its circumference and for the length of the bulk-head used. Therefore, with a proper design of the bulk-head B for stiiness, the large concentration of loads on said bulk-head is distributed over an exceedingly large area of the tunnel-lining equalling the distribution attained by the solid, deep, concrete bulk-heads now used but which are so inconvenient and expensive to move and rebuild and besides have other serious disadvantages.

Of course, I do not limit my improved bulkhead B to its application to cylindrical tunnels as illustrated in the drawing as the tunnel and bulk-head may have any particular cross-sectional shape to correspond with each other, nor to the thickness of the concrete joint between the bulk-head and the tunnel-lining although this latter should be as small as conveniently possible. My improvement makes for safety in using steel bulk-heads for tunnels and hasfthe advantage that the bulk-heads can be dismantled and used repeatedly. Y

As a further improvement, I coat or paint the surfaces'f'of the llanges llla and other parts of the bulk-head that contact with the concrete or grout with parain or other equivalent substance whichwill prevent the concrete from adhering thereto, said coating thus permittingA easy with structive to the conveyors and cars when thev material strikes them, or if this is avoided by using a, smallslope for .the chute, the material does not slideand the chutes become choked. Also, the small sloped chute must be very long and is always in the way of other work. The

novel chute I5 of my invention overcomes these difficulties andsaves time, space and expense, as, well as damage to` the conveyors. I amable to reduce the number of chutes required to at least one-third, none of which are required to be removed and Vreplaced when erecting the rings of the lining. My chute has an opening at each platform to receive the material thrown or-fed into the chute, thence the chute slopes downwardly at a sharp angle su'lcient to cause the material to move quickly to apoint midway betweenthisandthe n ext lower platform where the'slope of the chuteisreversed which slows up the fast movement of the material by stoppingvitand immediately ,starting it again down vopposite incline to the `next platform. The same checking of the momentum is repeated until nallythe material `is delivered into the .car or onto the conveyor with only substantially the same momentum that it hadk when it was rst dropped into the chute at the top platform. A gate is provided at thendelivery end of the chute to shut oi the ilow Iwhen a car is full; or the last incline of the chute may be in one or two parts and the end part may be hinged and raised up into a vertical position to shut-oiT theflow of the material; and the whole chute up to the top platform' maythereby be `used as a storage yfor the excavated material while a ring of the tunnellining is being erected, etc.

The chute of my invention may also be used for dropping mixed concrete or other mixtures ofY granular or large particles with a liquid from a height such as down the shaft to the tunnel to prevent and control the segregation of the ingredients.

Slightly raised strips may be placed flat on the inside of the bottom plates of the chute and at angles with the sides of the chute, but not extending entirely across to the sides. These strips also cooperate to retard the drop of the material. These strips retard the momentum of the solid particles of the mixture but because they are inclined and do not extend fully to the sides of the chute, the mortar of the concrete or the more finely divided portion of the mixture can flow along the sides of these strips and around their ends. The slope of the chute and the number and height of the strips and the angle which these make with the side of the chute are capable of wide and varied application, and itis these variations that control the flow of the ingredients to suit different mixtures and different conditions of placing and moving the mixtures, the slope of the different sections of the chute and the position of the strips may be arranged in such a manner as to be adjustable to the conditions encountered.

The metal beams, braces and other structural parts for supporting and bracing the bulk-head or header 23 with respect to the rest of the shield have been omitted from the drawing for the sake of simplicity and because these are merely engineering details which will vary with the sizev and shape of the shield.

It will be understood that this invention is not limited to the preferential embodiment herein illustrated and described and that modications and changes may be made therein in addition t0- those already indicatedwithout departing from the scope and spirit of the claims.

What I claim is:-

l. In combination, a lining and a bulk-head i construction for an excavated passage-way, said formed between said webs and their flanges being adapted to be iilled with concrete; and said bulkhead construction comprising a header surround? ed by a tubular shell, said shell having external annular ribs projecting towards the channels of thelining and seated in concrete anchored in said channels.

2. In combination, a lining and a bulk-head construction for Yan excavating passage-way, said lining comprising ring-like girders substantially .v fitting the cross-sectional shape of the passage,

said girders comprising flanged webs located with their flanges projecting inwardly, the channels formed between said webs and their flanges being adapted to be lled with concrete; and said bulkhead construction comprising a header surrounded by a tubular shell, said shell having external annular ribs projecting towards the channels of the lining and seated in the concreteanchored in said channels, said bulk-head construction consisting of parts adapted to be knocked down into.

portably separate parts.

3. In combination, a lining and a metal bulkhead construction for an excavated passage-way, said lining comprising ring-like metal channels adapted to be lled With concrete; and said metal bulk-,head construction filling the cross-section of said lining and having a plurality of external annular ribs projecting towards the channels of the lining and seated in concrete anchored in'said channels.

4., In an excavating device, in combination, a substantially tubular shield, means for forcing the shield through the ground, and a cutting edge at the mouth of said shield whose outer face slopes forwardly and inwardly, the tail end of said shield having an inner diameter which is not materially smaller than the corresponding inner diameter of the aforesaid cutting edge.

5. In an excavating device, in combination, a tubular shell, `means for forcing the shell endwise, and a cutting edge at the mouth of the shell whose face slopes forwardly and inwardly from the outside thereof, the tail end of the shell having an inner diameter which is not materially smaller than the corresponding inner diameter of the aforesaid cutting edge.

6. In an excavating device, in combination, an open-ended tubular shell, and means for forcing the shell endwise, the forward edge of the shell sloping from the outer'peripheral surface thereof forwardly and inwardly to form a cutting edge, the; opening at the tail end of the shell having substantially the same diameter as that at the cutting edge and being unobstructed to permit the erection therein of a tunnel lining with its outer peripheral surface closely adjacent the inner peripheral surface of the tubular shell.

'7. In an excavating device, in combination, a circumferentially continuous tubular shell, means for advancing the shell endwise, and wedging means on the forward end of the shell adapted to wedge and compress the material to be excavated radially outwardly during the advance of the shell, the body of the shell being dimensioned and arranged to maintain said compression.

8. In an excavating device, in combination, a tubular shell, a header supported and carried by said shell, means for forcing the shell endwise through the ground, wedging" means on the for-f ward end of the shell adapted to` wedge and compress the material to be excavated radially outwardly as the shell advances, the body of the shell being dimensioned and arranged to maintain said compression and to release same after the tail end of the shell has passed a predetermined point, the tail end of the shell being hollow and having an inner diameter which is not materially smaller than the corresponding inner diameter of the aforesaid wedging means.

WILLIAM F. TOWNSEND.

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