US 3217375 A
Description (OCR text may contain errors)
Nov. 16, 1965 c. H. KINNARD 3,217,375
APPARATUS FOR FORMING CONCRETE PLANKS OR SLABS HAVING ACOUSTICAL PROPERTIES Filed July e, 1962 7 sheets-sheet 1 ewa INVENTOR BY CLMBORNE H. KINNARD.
Nov. 16, 1965 c. H. KINNARD 3,217,375
APPARATUS FOR FORMING CONCRETE PLANxs 0R sLABs HAVING ACOUSTICAL PROPERTIES Filed July 6, 1962 7 Sheets-Sheet 2 CLAIBORNE; H. KINNARD ATTORNEYJ` NOV- 16, 1965 c. H. KINNARD 3,217,375
APPARATUS FOR FORMING CONCRETE PLANKS OR SLABS HAVING ACOUSTICAL PROPERTIES Filed July 6, 1962 7 Sheets-Sheet 3 NIK ATTORNEY Nov. 16, 1965 c. H. KINNARD 3,217,375 APPARATUS FOR FORMING CONCRETE PLANKs 0R sLABs HAVING ACOUSTICAL PROPERTIES Filed July 6. 1962 7 ShGebS-Shee 4 lOO 96 Q. m. F
INVENTOR ATTORNEYS Nov. 16, 1965 c. H. KINNARD 3,217,375
APPARATUS FOR FORMING CONCRETE PLANKS OR SLABS HAVING ACOUSTICAL PROPERTIES Filed July e, 1962 7 sheets-sheet s INV ENTOR www, @am YM?,
ATTORNE'YY Nov. 16, 1965 c. H. KINNARD 3,217,375
APPARATUS FOR FORMING CONCRETE PLANKS OR SLABS HAVING ACOUSTICAL PROPERTIES 7 Sheets-Sheet 6 Filed July 6. 1962 FIG. ll.
R m m w BY CLAIBORNB H. KINNARD Cba/M071 F16. lO.
, (mm f ATTORNEY'l C.HJGNNARD Nov. 16, 1965 3,217,375 APPARATUS Fon FORMING CONCRETE PLANKS 0R sLABs HAVING ACOUSTI CAL PROPERTIES 7 Sheets-Sheet 7 Filed July 6. 1962 CHN @ON NAN @ON bQN @ON @H NON WAN HHN INVENTOR HON CLAIBORNE H. KINNARD PON ATTORNEYS United States Patent O 3,217,375 APPARATUS FOR FORMING CONCRETE PLANKS R SLABS HAVING ACUS'IICAL PROPERTIES Claiborne H. Kinnard, Franklin, Tenn., assignor, by
mesne assignments, to Span-Deck, Inc., Franklin, Tenn.,
a corporation of Tennessee Filed July 6, 1962, Ser. No. 207,897 7 Claims. (Cl. 25-41) This invention relates to an apparatus for forming structural members of plastic material and is more particularly directed to the manufacture of hollow prestressed concrete members having acoustical properties and employing a nely divided insulating material as a core. This application is a continuation-impart of application Serial No. 129,214 which was tiled on August 2, 1961, now abandoned, as a continuation-in-part of an earlier application Serial No. 50,351, filed August 18, 1960, now abandoned.
One object of this invention is to provide an apparatus for forming an elongated hollow member of plastic material having a core of granular insulating material in which a bot-tom layer of plastic material is first laid and subsequently a column of granular material is extruded on top of the bottom layer simultaneously with the extrusion of layers of plastic material on top of and around the sides of the granular material.
A further object of this invention is to provide an apparatus for forming a hollow concrete plank or slab including a trough-like casting bed for receiving a bottom layer of acoustical concrete and a unitary frame adapted to move longitudinally of said bed including a rst hopper and a core mold for eXtruding a core of nely divided or granular insulating material and a second hopper for extruding structural concrete about the top and sides of the core.
Another object of this invention is to provide an apparatus for extruding concrete in an open trough-like casting bed having a vibrator mechanism adapted to vibrate the concrete Without contacting or vibrating any part of the casting bed.
A further object of this invention is to provide an apparatus -for continuously forming a hollow concrete plank or slab with or without reinforcing rods or prestressed reinforcing cables.
Another object of this invention is to provide a method and apparatus for forming a cored concrete structural member economically and in a minimum of time, and in which the core forming material is shaped simultaneously with the structural elements of the member and may be removed or left in the member as desired.
A further object of this invention is to provide an apparatus particularly designed for continuously forming a hollow concrete member about a core of linely divided, water-repellent, insulating material having a density of less than of that of the concrete.
Still another object of the invention is to provide a novel iform of prestressed concrete plank or slab which is characterized by its high structural strength, light weight, and superior sound absorbing and insulating properties.
Further objects and advantages of this invention will become apparent upon consideration of the following description, taken in conjunction with the accompanying drawings. In this connection, although certain apparatus has lbeen shown in the drawings for making two specifically different forms of hollow concrete planks, it is to be expressly understood that these drawings are for purpose reference should be had to the appended claims. as indicating the limits of the invention, for which latter purpose reference should be had to the appended claims.
In general, the apparatus of the present invention is so designed that, by a multi-stage procedure utilizing 3,217,375 Patented Nov. 16, 1965 ICC in succession different pieces of equipment, a plurality of hollow prestressed concrete planks are formed integrally as a continuous beam which, after a curing period, is cut transversely into planks of any desired length. The ap paratus comprises a stationary casting bed and an associated trackway of relatively great length and a number o-f devices which are mountable on and movable along the trackway in succession for performing the func tions of laying the bottom layer or wall of the beam, casting the top and side walls of the beam and simultaneously providing it with a core of granular insulating material, curing the casting, and then cutting it up into planks of the required length.
Referring now lto the drawings, wherein like reference characters indicate like parts throughout the several views:
FIGS. 1 and 2 are somewhat diagrammatic side elevation and top plan views, respectively, of the casting bed and trackway and two of the pieces of equipment used therewith in carrying out the invention in its presently preferred form, certain of the parts having been omitted in the interest of clarity, these views also being adapted to illustrate the rst stage of the method of the invention;
FIGS. 3, 4 and 5 are vertical sectional views, on an enlanged scale, taken substantially on the lines 3 3, 4 4 and 5 5, respectively, in FIGS. l and 2;
FIG. 6 is a side elevation of the same casting bed and trackway as that illustrated in FIGS. 1 and 2, but showing the casting machine and curing hoods utilized in the later stage of the method;
FIG. 7 is a front end view of the casting machine, including a vertical sectional view of the casting bed taken substantially on the line 7 7 in FIG. 6;
FIG. 8 is a longitudinal sectional view, on an enlarged scale, of the main part of the casting machine shown in FIGS. 6 and 7;
FIG. 9 is a rear end view of the casting machine, including a vertical sectional view of the casting bed taken substantially on the line 9 9 in FIG. 6, certain of the parts having been omitted in the interest of clarity;
FIGS. 10 and 11 are fragmentary side elevation and top plan views, respectively, partially in section, of the finishing screed portion of the casting machine which does not appear in FIG. 8;
FIG. 12 is a fragmentary perspective view illustrating the final stage of the method during which the cured casting is cut into planks of the desired length;
FIGS. 13 and 14 are perspective views of a plank made in accordance with the present invention showing, respectively, the top and bottom surfaces thereof, and indicating how the plank may be handled for transportation and installation purposes;
FIG. 15 is a fragmentary vertical sectional view showing how planks embodying the invention may be joined together to form a floor or ceiling;
FIG. 16 is a top plan view of another form of casting machine usable for carrying out the invention;
FIG. 17 is a longitudinal sectional view of the casting machine of FIG. 16 takebn substantially on the line 17-17 in the latter figure;
FIG. 18 is a rear end view, partially in section on the line 18 18 in FIG. 17, of the casting machine of the latter ligure; and
FIG. 19 is a fragmentary perspective view of a hollow concrete plank made by the apparatus illustrated in FIGS. 16-18.
The apparatus disclosed in FIGS. 1-12 is adapted to manufacture cored prestressed concrete structural members of elongated, generally rectangular shape, hereinafter referred to as planks, of the construction illustrated in FIGS. 13-15. In this embodiment of the invention, the
plank comprises a base layer or bottom wall 21 having a nominal width of 48 inches and a thickness or depth of from 1% to 1% inches, an upper layer or top wall 22 having a nominal width of 47 inches and a thickness approximately equal to that of bottom wall 21, and a plurality of laterally spaced webs 23, 24, and 26 which interconnect the bottom and top walls, the webs 23 and 26 forming the side walls of the plank while webs 24 and 25 form partitions which divide the interior of the plank into three longitudinally extending core openings 27, 28 and 29, each of which is 12 inches wide and from 41/2 to 4% inches deep. It will be understood, of course, that these dimensions are exemplary only, and that the invention is applicable to planks of various sizes.
Although the method and apparatus herein described may be employed to form planks wherein the bottom and top walls and the webs are all made of the same kind of concrete, the invention is particularly directed to a plank wherein the bottom wall 21 is made of lightweight dry mix of aggregate and cement of a composition similar to that employed in the manufacture of concrete blocks, commonly referred to as dry concrete, while the top wall 22 and webs 23-26 are made of a relatively dense, structurally strong, Wet concrete mix, the bottoms of the webs being securely bonded to the bottom wall in the finished product. Because of the porosity of the dry mix form- `ing the bottom wall, the acoustical and insulating values of the plank are improved and the overall weight thereof is reduced. A bottom wall of dry concrete also provides a better ceiling when the plank is used as an overhead structural member because nails may be driven into its surface, and openings for lighting fixtures and the like vmay be made therein, more easily than if a wet mix were used.
As shown best in FIG. 15, the plank 20 preferably includes a plurality of prestressed tendons or cables 30, suitable in size, strength and number to provide the desired amount of prestress in the plank, and may also incorporate reinforcing members, such as laterally extending rods 31, to meet the strength requirements of the job for which the plank will be used. The prestressing ele- Yments are all located in and bonded to those portions of the plank which are made of high strength wet concrete, i.e., the webs 23-26 and top wall 22 in the embodiment illustrated. The reinforcing members must also be so placed as to tie into the wet concrete even though portions thereof may pass through the structurally Weak, dry concrete bottom wall 21.
The core openings 27, 28 and 29 of plank 20 are preferably flled with a finely divided or granular, light-weight insulating material 32 which is incompressible or only slightly compressible, somewhat fluid and does not absorb water, such as vermiculite. A material which has been used with great success in carrying out the present invention is new water-repellent Zonolite brand vermiculite which is granular, dry, resilient and relatively freeflowing, and has a density of only about '7 pounds per cubic foot.
Since the advantages of the invention are due in part to the use of two different kinds of concrete, it should be understood that the terms dry concrete and wet concrete as used herein have the following meanings. By dry concrete is meant a substantially non-fluid mixture of aggregate, cement and water having a density of approximately 65 pounds per cubic foot, little structural strength and a substantially zero slump value. For eX- ample, a typical dry concrete mix which has been used in carrying out the invention consists of 820 pounds of expanded shale, 188 pounds of cement and sufficient water to bring the mix to a damp, slightly sticky but still granular consistency. By wet concrete is meant a quite fluid mix having a density of 110 pounds per cubic foot or more, a slump value in excess of 5 inches and a 28-day strength of 5000 p.s.i. or greater. A typical wet concrete mix suitable for use in practicing the invention consists of 4 730 pounds of a to inch limestone, 730 pounds of 1A inch to dust of expanded shale, 517 pounds of cement and sufficient water to give a 6 inch slump.
Referring now to FIGS. l-5, the stationary portion of the apparatus illustrated comprises a trough-like casting bed 33 and an associated trackway 34 which are supported on a permanent base 35 in any suitable manner, as by transversely extending beams 36. The bed 33, which has a length in excess of 300 feet, is located centrally between the rails 37 of trackway 34, which rails extend beyond the ends of the bed and are connected at their own ends to a pair of headers or bulkheads 38 which, in combination with the rails, form a prestressing bed. Each bulkhead 33 is provided with a plurality of suitably positioned openings 39 through which the ends of the prestressed tendons rnay be passed during prestressing.
The casting bed 33, which is open at both ends, cornprises a base 46 (FIG. 3) having a pair of longitudinally extending horizontally disposed side flanges 41, a bottom lining 42 the upper surface of which is shaped to conform to the desired configuration of the bottom surface of the plank to be cast, and a pair of removable side walls 43 which are also so shaped as to conform to the desired configuration of the side surfaces of the plank. The side walls 43 are made of metal and are provided with inverted L-shaped bottom flanges 44 which rest on and embrace the flanges 41 of base 40 and are detachably connected thereto in any suitable manner, as by pins 45 which are fixed to the base 40, pass through holes 46 in flanges 44 and receive wedge-shaped cotters 47. The side walls 43 converge upwardly toward one another at a slight angle, and are provided with inwardly projecting ribs 48 which form longitudinally extending keyways in the side walls 23 and 26 of the plank, as indicated at 49 in FIGS. 13-15, and with outwardly turned upper flanges 50 which establish the plane of the upper surface of top wall 22 of the plank.
The bottom lining 42 of the casting bed may be Amade of any suitable material which can be formed to the desired shape and will provide a smooth surface to which the concrete constituting the bottom wall of the plank will not adhere. Although fiberglass has been used satisfactorily for this purpose, -it is preferable to form the lining 42 of metal, such as steel, and to coat it with a releasing agent prior to each casting operation. As shown Ibest in FIG. 3, lining 42 is provided with rounded edges 51 and a pair of longitudinally extending upwardly pro- 1jecting ribs 52 which form, respective-ly, the bottom edges 53 and the decorative joint-simulating indentations 54 in the bottom surface of the plank (FIGS. 14 and 15).
Assuming that the side walls 43 of the casting bed 33 are in place and that the upper surface of lining 42 and the inner surfaces of side walls 43 have been coated with a suitable releasing agent, the first stage of the method of the present invention involves the formation in the bed of a compacted layer of dry concrete adapted to form the bottom wall of the beam which is ultimately cut into a plurality of pre-stressed planks of the construction illustrated in FIGS. 13-15. For this purpose, there are provided the two pieces of movable equipment indicated generally at 55 and 56 in FIGS. 1 and 2, 55 being a hopper unit by which the dry concrete mix is deposited in the bed and preliminarily leveled, while 56 is a roller unit which serves to compact the dry yconcrete into a non-fluid, stable layer 21 of predetermined thickness and to simultaneously `form in the upper surface of the layer a plurality of longitudinally extending, laterally spaced depressions or grooves 57, 58, 59 and 160 (see FIGS. 2 and 5) which ultimately receive the lower ends of the wet concrete side wall and partitioning webs 23, `24, 25 and 26, respectively, of the finished plank.
The upper unit 55 comprises an open framework 61 having `four supporting wheels 62 which are adapted to roll on the rails 37 of trackway 34. Removably mounted on framework 6]. is a hopper `63 of any suitable capacity which is rectangular in cross section and of a ,s E width slightly less than the distance between the upper ends of side walls 43 so that the lower end of the hopper may project downwardly into the bed and deposit the dry concrete mix on the bottom lining 4t2. The hopper 63 'may he adjusted vertically with respect to framework 61 in any suitable manner, or hoppers of different heights may be used interchangeably on the framework, so that the bottom edge "64 of the -rear wall of the hopper will serve as a level or screed to establish the initial thickness of the dry concrete layer 21. The edge i64 may, if desired, be provided with a plurality of removable Scrapers 65 which form the grooves 57-60 in the upper surface of the dry concrete. The hopper framework 61 also carries a pair of rollers 66, positioned to the rear of the lower end of 4hopper 63 and closely adjacent to the bed side walls 43, which effect an initial compaction of the side edges of the dry concrete layer in the areas defined by the -gooves 57 and i610. The hopper unit l55 may be propelled along trackway 34 either manually or by any suitable for-m of motor driven mechanism.
The roller unit 56 also comprises an open framework 67 having supporting wheels 68 adapted to roll on the trackway rails 37, the two front wheels preferably being driven through a suitable `chain and sprocket mechanism 69 by a motor 70 mounted on top of framework 67. A roller 71 having an axle 7'2 which extends transversely of the casting bed is connected to yframework `617 by a pair of lever arms '713 the rear ends of which receive axle 72 while the front ends are pivotally mounted on a transversely extending member 74 of the framework. Like hopper 63, roller 7.1 is of a Width only slightly lless than the distance between the upper ends of bed side walls 43, and is provided with a plurality of circumferential laterally spaced ribs 7:5, 76, 77 and 78 of proper size and position to enter the grooves 57, 53, 59 and 60, respectively, in the surface of the dry concrete layer 21. The Weight of roller 71 may be varied, as by filling the roller with water, so as to finally compact the dry concrete to whatever thickness may be desired for the bottorn Wall of the finished plank. In order to raise and hold roller 71 in an elevated position vat times other than when it is being used to compact the dry concrete, a pair of chains 79 are connected to arms 73 and extend upwardly to a bar i8() which is in turn connected by cables 31 to a winch `812 mounted on top of framework 67. When the roller is raised, the motor driven roller unit may be used for such purposes as propelling the hopper unit 55 and pulling the prestressing cables 30 through the bed.
In order to form the dry concrete bottom layer in the casting bed, the hopper unit S is first placed in position on the trackway -34 at the left-hand end thereof as viewed in FIGS. l and 2, which end of the apparatus will be regarded as the rear end for direction purposes. Hopper 63 is then lled with an appropriate quantity of dry concrete mix and moved forwardly along the trackway so as to deposit on the bottom lining '42 of the casting bed a layer 21 of dry concrete of a thickness established by the height of the bottom edge 64 of the rear wall of the hopper. If desired, hopper 63 may be provided with a gate valve 83 adjacent the 4lower end thereof for controlling the delivery of concrete into the bed, although such a valve is not essential. As the hopper unit 55 moves forwardly, the scrapers 65 form the grooves SL60 in the upper surface of the concrete and the trailing rollers 66 compact the side edges of the concrete in the areas immediately adjacent the bed side 'walls 43.
IBefore roller unit 56 is mounted on the trackway and placed in operation, whatever reinforcing elements are required in the finished plank, such as the rods 31, are placed in the `bed by hand. As indicated in FIGS. 2 and 4, each rod 31 is pushed do'wn into the dry concrete layer 21 until the upper surface of the rod is substantially ush with the bottoms of `grooves 57-60, leaving the bent ends of the rod in upwardly projecting positions closely adjacent to side walls 43. The roller unit 56 is then placed on the trackway and moved back and forth over that portion of the dry concrete layer in which the reinforcing elements have been placed until the concrete has been compacted to the proper degree. In this connection, it will be noted that, due to the convergence of side walls @3, the portion of roller 71 which contacts the concrete is of less lwidth than the concrete layer itself so that the roller ribs '75 and 7i8 compact only the inner portions of grooves 57 and i60 and do not roll those portions in which the upturned ends of the reinforcing rods 31 are located. It will `also be noted that, as shown in FIG. 5, the rolling operation leaves the upper surfaces of rods 31 exposed in each of grooves 57-460, a feature which facilitates the subsequent operation of pulling the prestressing cables through the bed, and also permits the rods to become bonded to the wet concrete when the latter is poured.
As soon as the dry concret-e layer has been laid in the casting bed, the reinforcing elements have been placed therein and the layer has been rolled and compacted as above described, the next stages of the method may be carried out by the equipment illustrated in FIGS. 6l1. These stages involve placement and tensioning of the prestiessing members, molding of the vermiculite cores and simultaneous casting therearound of the wet concrete side walls, partition webs and top wall of the plank beam, and curing of the casting.
As indicated in FIGS. 6 and 7, prestressing cables 3) are passed through the openings 39 in the rear bulkhead 38, pulled through the casting bed 33, passed through the openings 39 in the front bulkhead 38 and anchored at their front ends in any suitable manner. In the embodiment illustrated, six prestressing cables are used, four of them being positioned in a substantially horizontal plane a short distance above the dry concrete layer 21, one in the vertical plane of the center line of each of grooves 57-69, while the other two are at an elevation such as will place them in the top wall 22 of the finished plank in the same vertical planes as the lower cables which overlie grooves 58 and S9. As previously mentioned, pulling of the cables through the bed may be readily accomplished by attaching their front ends to a transverse member of the rolling unit framework 67 and propelling the latter from the rear end to the front end of the trackway 34, the exposed portions of reinforcing rods 31 in grooves 57-60 serving to support the cables and enable them to be pulled easily without disturbing the rolled surfaces of the ydry concrete at the bottoms of the grooves. After the cables have been placed and anchored at their front ends, they may be prestressed to the desired tension in conventional manner by means of jacks applied to their rear ends.
When the prestressing cables are in place, formation of the plank beam may be completed by means of the apparatus indicated generally at 84 in FIGS. 6e9, herein referred to as the casting machine. As shown, the casting machine 84 comprises an open framework 85 adapted to travel along trackway 34 on wheels S6 and supporting a forward hopper 87 for feeding vermioulite to three core molds 88, and a rear hopper 89 and associated feed chute 90 for distributing Wet concrete on top of and along the sides of core molds 88 so as to form the top wall 22 and the side wall and partition webs 23-26 of the plank beam. The casting machine also includes a finishing screed assembly 91 which is connected to and towed by the framework 85.
In the structure illustrated, the casting vmachine framework includes front and rear standards 92 and 93 from which depend the bearings of wheels 86, upper and lower longitudinal stringers 94 and 95 and front and rear tie beams 96 and 97 interconnecting the standards 92 and 93, and front and rear support beams 98 and 99 which extend between and are fixed to lower stringers 95. Framework 85 is also provided with a transversely extending beam 100 positioned forwardly of front standards 92 adjacent the lower ends thereof to which are detachably connected a plurality of cable guide hangers 101 and 102 having hook-like fingers 103 adapted to engage and support the prestressed cables 30 at the proper heights as the wet concrete portions of the beam are cast.
As shown best in FIGS. 8 and 9, each core mold 88 comprises a top wall 104, a pair of side walls y105 and a front wall 106, the rear end being open and the lower edges of the side walls preferably being bent inwardly toward one another as indicated at 107. The core molds 8S are supported in laterally separated positions by a bedplate S to which the top walls 104 of the molds are welded or otherwise fixed, the bedplate in turn being supported at its front and rear ends by welded connections to the bottom edge of front support beam 9S and the front wall 109 of feed chute 90, respectively. As indicated in FIG. 8, bedplate 108 is inclined downwardly from its front edge to its rear edge so that the inwardly convergent portions 107 of core mold side walls 105 dig into the dry concrete layer 21, at least throughout the portions thereof which lie to the rear of a vertical plane through the bottom edge of front wall 109 of chute 90. Vermiculite is delivered to core molds 88 from hopper 87 through a depending vertical conduit 110 in which is positioned a vane-type shut-off valve 111 and which feeds into three outlet channels 112 separated by tapered dividers 113. The lower end of each outlet channel 112 is of substantially the same width as, and is welded to, the top wall 104 of one of the core molds, passing through bedplate 108 and opening directly into the interior of the core mold.
The wet concrete hopper 89 -is supported by the casting machine framework 85 in any suitable manner to the rear of vermiculite hopper 87 and above feed chute 90, the hopper 89 having an outlet 114 which is controlled by a flap valve 115 and is adapted to deliver wet concrete into, and to maintain a predetermined level of concrete in, the chute 90. Feed chute 90 has a funnelshaped upper end portion 116 and a depending, rearwardly inclined portion 117 bounded by the previously mentioned :front wall 109, a substantially parallel rear wall 118, and a pair of side walls 119 which together form a delivery channel of rectangular cross section having a width only slightly less than the distance between the upper edges of side walls 43 of the casting bed. The lower edge of rear wall 118 of chute 90 terminates a predetermined distance above the top walls 104 of core molds 88, and is welded or otherwise fixed to the lower edge of rear support beam 99. The lower ends of chute 90 and -outlet channels 112 'of the vermiculite hopper 87 are also strengthened and supported by a pair of fiat plates 120 which extend longitudinally between and are xed to front and rear support beams 98 and 99.
The iiow of wet concrete from chute 90 onto and around core molds 88 is controlled both by the level or head of concrete in the chute and by manually operable swinging gate valve 121 located in the inclined portion of the chute. As previously mentioned, the level of concrete in the chute lis controlled by flap valve 115 at the outlet of hopper 89, which valve is preferably `operated automatically by a solenoid 122 energized Vin known manner by the electrical contacts of a level or pressure responsive device .mounted on chute 90, although it may be operated manually, if desired. This mainainence of a substantially constant level of wet concrete in the chute is necessary in order to insure a steady rate of flow of the concrete onto and around the core molds.
The volume of ow of the wet concrete is controlled manually by the operator of the casting machine, in relation to the speed :of travel of the machine along the casting bed, by means of gate valve 121. The machine is propelled by the two rear wheels 86 which are driven by a motor 123 mounted on framework 35, through a reducing gear 124 and a chain and sprocket transmission 125.
As it moves forwardly along the bed, at a rate which may vary between 4 and l0 feet per minute, the operator observes the rate at which the wet concrete is deposited in the casting bed and adjusts that rate to provide a casting of the desired height by opening or closing valve 121 by means of a hand wheel 126. The hand wheel is geared to a threaded shaft 127 which carries a travelling nut 128 having a pin and slot connection to a lever arm 129 fixed to a transversely extending shaft 130 which is mounted on the rear wall 118 of chute 90 and carries the valve 121.
In order to level the upper surface of the wet concrete as it is deposited in the casting bed, :a forming screed is provided consisting of a horizontal plate 131 which is mounted directly behind the bottom edge of rear wall 118 of chute 90 by means of an angle iron bracket 132 t-o which it is welded and which is in turn welded or otherwise fixed to the vertical portion of rear support beam 99. Screed plate 131 extends transversely across the casting bed with its bottom surface slightly above the plane of the upper fianges 50 of bed side walls 43, but is slightly narrower than the distance between said side walls. In order to permit the wet concrete to be deposited in the bed up to the level established by screed plate 131 without overflowing the side walls 43, a pair of sealing plates 133 are fixed to support plates 120 outboard of the side edges of screed plate 131 and so positioned as to extend downwardly below the upper flanges of the side walls, in Contact with the inner surfaces 'of said Walls, as shown best in FIG. 9.
ln order to assist in maintaining a proper flow and distribution of the wet concrete as it is discharged from chute onto and around core .molds 88, an eccentrically weighted vibrator shaft 134 is mounted in bearings 135 on the horizontal portion of rear support beam 99, the shaft being driven through a belt and pulley transmission 136 by a motor 137 which is suitably mounted on the framework 85. Vibration is thus transmitted to support beam 99 and all of the elements fixed thereto, but is not transmitted to the side Walls 43 or any other portions of the casting bed 33.
From the foregoing description of the casting machine, it will be evident that, when the hopper 87 is filled with vermiculite and the shut-off valve 111 is open, the vermiculite will descend through outlet channels 112 into the core molds 88 and be deposited on top of the dry concrete layer 21 in the shape to which it is formed by the top and side walls of the molds. As the casting machine is moved forwardly, wet concrete from hopper 89 is delivered by chute 90 onto the top walls 104 of the core molds and into the spaces between the bed side walls 43 and the adjacent si-de walls of the two outer core molds, and between the adjacent side walls of the molds themselves, so as to form the top wall 22, side walls 23 and 26 and partition webs 24 and 25 of the plank beam which is being cast. The wet concrete fills the grooves 57-60 in the upper surface of the dry concrete layer 21, producing a firm bond between the two kinds of concrete, and also surrounds and becomes bonded to the prestressed cables 30 and the reinforcing rods 31. As the wet concrete leaves the chute 90 it is leveled by screed rplate 131 at a height slightly above the desired elevation of the finished plank beam so that, when the core molds 8S move forwardly with respect to the deposited concrete, there is sufficient concrete avaliable to fill the voids left by the walls of the core molds.
Thus, as the vermiculite cores are extruded through the open rear ends of core molds 88, their form is maintained by the shaped concrete walls and partition webs 22-26. Because the vermiculite cores are made of a material which is relatively incompressible and water-repellant, the cores will not collapse after they have been extruded from the molds, nor will they absorb water from the adjacent wet concrete walls. On the other hand, since the vermiculite is very much lighter than concrete, special provisions must be made to prevent the wet concrete from displacing the vermiculite and producing distorted cores. In addition to the critical dimensioning hereinafter mentioned, displacement of the vermiculite is also prevented by insuring that the core mold side walls 105 cut into the dry concrete bottom wall 21 of the plank beam and thereby prevent the wet concrete from flowing beneath said side walls into the interior of the molds and resisting, or even eventually cutting off, the flow of vermiculite into the molds.
In order to provide the casting with a smooth upper surface level with the upper edges of bed side walls 43, the previously mentioned finishing screed assembly 91 is connected to and trailed behind the casting machine, :as indicated generally in FIG. 6. As shown in detail in FIGS. and l1, the assembly 91 includes a pair of shoes 138 adapted to slide on the upper flanges 50 of bed side walls 43 and to support between them a transversely extending screed plate 139 the bottom of which is substantially flush with said upper flanges, a rotatable shaft 140 which is mounted in front of and above plate 139 and provided with a plurality of radially extending concrete stirring fingers 141, and an arcuate dam member 142 which is positioned closely adjacent the rear portion of the path of the ends of fingers 141 and has its lower edge welded or otherwise fixed to the front edge of screed plate 139. Shoes 138, plate 139, shaft 140 and dam 142 are towed by the casting machine by means of a pair of arms 143 which are pivotally mounted at their rear ends on the ends of shaft 140 outboard of bed side walls 43. The forward ends of arms 143 are also pivotally mounted on a pair of outwardly extending stub axles 144 on which are fixed wheels 145 adapted to travel on the rails 37 'of trackway 34 just forwardly of the rear wheels 86 of casting machine framework 85, the axles being journalled in bearings which are suspended from and fixed to the lower stringers 95 of said framework. Shaft 140 may be rotated in any suitable manner, as by means of a chain and sprocket drive 146 from axles 144.
As the finishing screed assembly is pulled along by the casting machine, the screed plate 139 scrapes the upper surface of the wet concrete and smooths it level with the upper flanges of bed side walls 43, the excess concrete being caught and carried along by the dam 142 while continuously stirred or agitated by fingers 141 to prevent solidilication thereof. The excess concrete is thus available to fill in undesired depressions in the upper surface of the plank beam as the casting machine moves forwardly.
Continuous travel of the casting machine along the full length of the casting bed thus produces a continuously formed prestressed concrete plank beam of uniform cross section having relatively smooth top, bottom and side surfaces of the desired configuration and three hollow cores filled with vermiculite. Since it is desirable to provide the casting with means for facilitating handling of the finished planks, workmen may follow along behind the finishing screed assembly 91 and manually insert in the still soft upper surface of the wet concrete, at any desired intervals, inverted U-shaped lifting eyes 147, as indicated at the left-hand end of FIG. 6. Each end of the beam may also be provided with a transversely extending lifting strap 148 (FIG. l2) for a purpose hereinafter described.
The next stage of the method is to cure the casting until the wet concrete sets to the desired strength so that the prestressed members may be released and the planks removed from the casting bed. Accordingly, after the casting machine has been removed from the trackway 34, a plurality of curing hoods 149, which are normally maintained in elevated positions above the casting bed 33 by cables 150, are lowered so as to cover the casting, as indicated in FIG. 6. Each hood 149 may comprise a metal frame having a covering of any suitable material for confining steam therebeneath and a pair of flexible aprons 151 which are adapted to close the space between the bottom edges of the hood frame and the floor on which the bed and trackway are mounted. When all of the curing hoods have been lowered into place, steam may be supplied to the hood-enclosed space through perforated pipes 152 which extend transversely beneath the casting bed. Although super-heated steam may be used for the curing operation, it has been found that, in practicing the present invention, the casting may be cured to the desired release strength of approximately 3500 p.s.i. in from l2 to l5 hours by using live steam at atmospheric pressure.
After the casting has been cured, the hoods 149 are raised, the prestressed tendons 30 are cut loose from the bulkheads 38 so as to transfer the stress to the wet concrete portions of the plank beam, and the side walls 43 of the casting bed are removed preparatory to cutting the beam into planks of the desired length. However, before cutting, it is preferable to lift the beam at one or both ends by straps 148 suiiiciently to enable placement of wooden battens 153 (FIG. l2) beneath the beam at intervals along the length thereof so as to raise it off the bottom lining 42 of the bed far enough to permit the beam to be cut all the way through from top to bottom without damaging the bed lining. The cast beam may then be cut transversely into planks of any desired length by means of a motor-driven rotary diamond saw 154 which is mounted on a carriage 155 adapted to be supported on and travel along trackway 35 on wheels 156, as illustrated in FIG. l2.
After the casting has been sawed into individual planks, the latter may be lifted out of the bed and transported to a storage location, or placed on a truck for delivery to a construction site, by a crane or other lifting device of suitable construction having cables 157 equipped with hooks 158 for engaging the pick-up eyes 147 in the top walls of the planks, as indicated in FIGS. 13 and 14. The vermiculite cores 32 preferably remain in the concrete planks to improve the acoustical and insulating qualities of the latter, particularly because the extreme lightness of the vermiculite does not appreciably affect the total dead weight of the planks. On the other hand, if a hollow beam having empty cores is desired, as when the plank is to be used in multi-story building work where insulation is not of great importance, or in the case of structural members having depths on the order of 12 inches or more in which vermiculite lled cores would provide an unnecessarily large amount of insulation, the vermiculite may be removed from the finished plank in any suitable manner, in which instance the vermiculite may be economized by reuse in the formation of another plank.
The planks 20 may be used for a variety of structural purposes, such as th-e formation of a combined oor and ceiling in a building. When so used, a plurality of planks may be assembled on suitable supports in the manner indicated in FIG. l5 with their lower side edges 53 in abutment with one another. The joints between adjacent planks can then be finished by first caulking the bottoms of the V-shaped spaces between the side walls with asbestos rope 159 and then filling the remainders of said spaces, including the keyways 49, with grout keys 160 of a suitable cement-sand composition. In the event that the upper surfaces of the planks are to be covered by a structural topping, such as concrete, the top of the plank beam may be striated or roughened, as indicated in FIG. 13, before the curing operation. In an installation such as that illustrated in FIG. l5, the top walls 22 of the planks provide a structurally strong supporting surface or floor, while the dry concrete bottom walls 21 and vermiculite cores 32 provide a ceiling of superior acoustical and insulating properties which also has a decorative appearance, as shown in FIG. 14, produced by the longitudinally extending indentations 54 in the bottom walls and the similarly shaped joints between the rounded bottom edges 53 of the planks.
Although the use of sand cores in the art of molding hollow concrete products is old, the sand is never left in the product after the concrete has set, but is either poured or washed from the interior in order to leave the product hollow. Since the density of sand is about 100 pounds per cubic foot and the density of concrete is about 140- 150 pounds per cubic foot, sand remaining in the concrete product would merely increase the weight unnecessarily without improving the performance or function of the product. On the other hand, a lightweight insulating material such as vermiculite, which has a density of only about 7 pounds per cubic foot, may remain in a concrete member without materially affecting the total weight of the member, while at the same time considerably improving the insulating and acoustical properties thereof.
However, because of the vast differences in density of sand and vermiculite, the problems of handling them as core materials for the continuous formation of concrete members is quite different. The density of sand is sufficient to prevent the fluid concrete from materially displacing the sand. On the other hand, being about twenty times denser than vermiculite, concrete readily displaces the vermiculite unless the casting procedure is carefully controlled. Since the method and apparatus of the present invention are designed primarily for the continuous formation of concrete members about cored of a lightweight, Water-repellent, insulating material, such as vermiculite, the prior art procedures utilizing sand cores do not provide a solution for the problems inherent i-n the use of vermiculite as a core material.
In order to continuously form a concrete member about a core material as light as vermiculite without distortions, certain functions must be accomplished and controlled. As the fluid wet concrete is deposited on top of the vermiculite cores and on opposite sides thereof, equal pressure of the concrete on the said three surfaces of the vermiculite must be maintained in order that there may be no displacement of the vermiculite on account of excessive or uneven side pressure or excessive or uneven downward pressure, any of which would produce distortions in the member. As an extreme result, irnbalance in pressures can result in cutting off entirely the gravity flow of vermiculite from its hopper 87, thereby eliminating any cores in the product. As a part of the control of pressure, it is necessary to protect the vermiculite from the downward pressure of the fluid wet concrete flowing from the feed chute 90 and to convert an exact part of this downward pressure into a horizontal force sufllcient to ca-use the fluid concrete to be pushed from the rear edges of the core molds S8 smoothly and evenly so that it is lightly deposited on top of and on both sides of the vermiculite under no vertical pressure other than its own weight.
The accomplishment of these purposes is the result of critical dimensions which (l) maintain a balance of the pressure of the fluid concrete on the surface of the vermiculite, and (2) retain the fluid concrete on the metal core molds 88 for a distance sufficient to protect the Vermiculite from the downward pressure of the concrete flowing from the feed chute 90, but not so long as to permit the concrete to collect on the core molds and flow unevenly therefrom. By said critical dimensioning, what is accomplished is that, at the moment the fluid concrete comes into contact with the vermiculite, the concrete is subject only to horizontal pressure suficient to cause it to flow off and away from the metal core molds, and there is exerted on the vermiculite vertical pressure equal only to the weight of the concrete being deposited.
It has been found in actual practice that, for core molds 88 having a height of about 5 to 6 inches, and with the forming screed 131 being located about 1% inches above the tops of the core molds and slightly above the level of the tops of casting bed side walls 43, the rear edges of the core molds sho-nld extend approximately 3% inches behind the rear edge of the forming screed plate 131 and. approximately 71/2 inches behind the front edge of the latter. The level of the wet concrete in the feed chute 90 must also be kept substantially constant in order to produce an even feed of fluid concrete so that, in relation to the distance that the concrete is retained on the metal core molds, the horizontal force produced is sufficient for proper deposit of the concrete as above set out. Such a constant level in the feed chute 90 is maintained by the use of an upper hopper 89 which is so controlled, either automatically as above described or manually, as to deliver concrete into the chute whenever the level drops below a predetermined point.
It is also necessary to note that the vibrating mechanism, including shaft 134 and bearings 135, should be so mounted as not to transmit vibration to the side walls 43 of the casting bed. lf the side walls 43 were to be vibrated, the wet concrete would be forced to the bottom of the casting bed, and, after the vermiculite had been extruded from the rear ends of the core molds 88, the gravitating vibrated concrete would force the much lighter vermiculite upwardly through the top concrete wall 22 of the beam.
Another important feature Vof this invention resides in the fact that no bottom wall is employed in the core molds 88, the dry concrete layer 21 on which the vermiculite is deposited being utilized as the fourth side of each mold. Were the core molds themselves four-sided, the surface friction of the molds would seriously restrict the deposit of vermiculite and thereby upset the balance of resistance of ver-miculite to the pressure of the fluid concrete. In accordance with the invention, rather than the surface friction of a lfour-sided mold restricting the flow of vermiculite, the surface friction of the dry concrete on which the vermiculite is deposited by a threesided mold riding' on top of the concrete operates to cause the vermiculite to remain where deposited so as to produce a continuous vermiculite core.
It has also been found in the practice of this invention that the core molds 88 should be either supported in -a downwardly inclined position, or gradually tapered in height, from front to rear in order to compact the vermiculite material yfrom the time it is discharged from the hopper 87 until it is extruded between the wet concrete walls and partition webs 22-26. Satisfactory results have been obtained using core molds 60 inches` long wherein the top walls 104 have a height above the dry concrete bottom layer 21 of 6 inches at their front ends and 5 inches at their rear ends, and the inwardly bent bottom edges 107 of the side walls 105 cut into the layer 21 to a depth of approximately 1A inch.
The apparatus illustrated in FIGS. lll-16 represents an earlier and simpler form of the invention than that of FIGS. l-l3, and is adapted to produce a concrete member 200 of the construction illustrated in FIG. 17, having only a single core.
As shown in FIGS. 14-16, the casting bed 201 comprises a bottom Wall 202, side Walls 203 and 204 and an end wall 205. The hopper frame 206 employs a pair of side longitudinal angle members 207 and 208. The horizontal bottom flanges or runners 209 and 210 of the angle `members are adapted to slide along the top edges of the side walls 203 and 204 and are guided by rollers 211 and 212. A transverse supporting plate 213 connects the rear ends of the angle members 207 and 208, supports the rear wall 214 of the wet concrete hopper 215, and acts as a screed to level the top surface of the concrete member 200. In this embodiment, the side walls of the concrete hopper 215 extend forward to a common front wall 216 with the vermiculite hopper 217. The bottom portion of the front wall 216 also extends downward to close the front end of the core mold 218. The
outlet 219 of the hopper 217 communicates with the single core mold 218 in substantially the same manner as in the first embodiment. Mounted on the top wall 220 of the core mold 218 are three interesting sloping surfaces 221, 222 and 223 which uniformly distribute concrete from the hopper 215 upon the top mold wall 220 and along the outside of the mold walls 224 and 225. The rearwa-rd sloping surface 221 is attached to the rear wall 214 of the concrete hopper 215 by means of a supporting bar 226.
In this apparatus, the bottom layer of dry concrete 227 is first laid on the bottom wall 202 of the casting bed 201 in any convenient manner and leveled to a uniform height, approximately 1A inch above the bottom edges of the side walls 224 and 225 of the core mold 21S and substantially flush with the bottom edge of the front wall 216. The hopper frame 206 is then placed in operative position on the casting bed 201 with the rear open end of the core rnold 218 abutting the end Wall or prestressing bulkhead 205. With the hopper 217 and the core mold 218 filled with vermiculite and the concrete hopper 215 lled with wet concrete, the hopper frame 206 is moved forward along the casting bed 201 in such a manner that the vermiculite core 228 and the top concrete wall 229 and outer side walls 230 are simultaneously extruded to form a plastic concrete article 200 having a single core. Although no reinforcing bars o-r cables are disclosed in the embodiment of FIGS. l4-17, it will be understood that either reinforcing bars or prestressed cables, or bot-h, may be employed therein. After the plastic concrete has set, again the vermiculite preferably remains as an insulating core, but may be removed if desired. FIG. 17 discloses a portion of a completed article 200 having a hollow core with the vermiculite removed.
The critical dimensions of the core mold and screed, previously discussed, are also applicable to the core mold 218 and the screed 213 of this embodiment in order to obtain a balanced extrusion between the concrete walls and the vermiculite core.
Although the planks of the present invention are described and claimed herein as having top and bottom walls made of wet and dry concrete, respectively, it will be Iunderstood that the terms top and bottom refer to the plank in the position in which it is cast, and that the nished plank may be installed in various positions, including the vertical, wherein the wet and dry concrete walls no longer form the top and bottom, respectively, of the plank.
It will also be apparent to those skilled in the art that various changes may be made in the details of construction of the apparatus, the specific procedures of the method and the size, shape and arrangement of the elements of the product without departing from the inventive concept. The scope of the invention is therefore not limited to that which is shown in the drawings and described in the specification, but only as indicated in the appended claims.
What is claimed is:
1. Apparatus for manufacturing an elongated cored concrete structural member comprising:
a horizontal casting :bed having longitudinally extending bottom and side walls,
means for forming a layer of concrete on the bottom wall of said bed,
a frame adapted to be moved longitudinally of said bed,
a core mold depending from said frame within the side walls of said bed, said mold having longitudinally extending top and side walls, an open lbottom and an open end, the lower edges of said side walls being in contact with the layer of concrete on the bottom wall of said bed,
means for feeding a lightweight, finely divided material to the interior of said mold and thereby depositing directly onto said layer of concrete a longitudinally extending core of said material,
means for simultaneously depositing fluid concrete on top of said mold and between the side walls of said mold Vand the side walls of said bed in contact with the portions of said layer of concrete lying outwardly of the side walls of said mold, and
means for moving siad frame longitudinally of said bed in a direction opposite the open end of said mold continuously during the feeding of said core material and the deposit of said fluid concrete,
whereby said core material is continuously extruded through the open end of said mold and simultaneously covered on the top and sides thereof by said fluid concrete while the side walls of said mold prevent the fluid concrete from iiowing laterally inwardly and displacing the core material deposited on said layer of concrete.
2. Apparatus as defined in claim 1 wherein the means for feeding the core material comprises a first hopper mounted on top `of said mold, said hopper having an outlet communicating with the interior of said mold adjacent the end thereof opposite said open end, and
the means for depositing fluid concrete comprises a second hopper mounted over said mold between said first hopper and the open end of said mold, and means for distributing fluid concrete from said second hopper to a uniform height over the top wall of said mold and between the side walls `of said mold and the side walls of said bed.
3. Apparatus for manufacturing an elongated cored concrete structural member comprising:
a horizontal casting bed having longitudinally extending bottom and side walls, l
means for forming a layer of concrete on the bottom wall of said bed,
a frame adapted to be moved longitudinally of said bed,
a core mold carried by said frame having longitudinally extending top and side walls, an open bottom and an open rear end, said core mold having a width less than that of said bed and extending downwardly into said bed with its top wall below the upper edges of the side walls of said bed and with the lower edges of its side walls in contact with the layer of concrete on the bottom wall of said bed,
a first hopper mounted on said frame adjacent the front end of said mold having an outlet communicating with the interior of said mold for supplying core forming material thereto,
a second hopper mounted on said frame a fixed distance behind said first hopper having an outlet of substantially the same width as and opening into said bed, the bottom edge of the rear wall of said second hopper being located above the top wall and forward of the open rear end of said mold, said second hopper being adapted to deposit uid concrete onto the top wall of lsaid mold and into the spaces between the side walls of said mold and the side walls of said bed,
a screed for shaping the upper surface of said fluid concrete extending Irearwardly from said bottom edge of the rear wall of said second hopper to a point closely adjacent to but forward of the rear edge of the top wall of said mold, and
means for moving said frame longitudinally of said bed :in a direction opposite the open rear end of said mold continuously during the supply and deposit of the core forming material and fluid concrete,
whereby said core material is continuously extruded through the open rear end of said mold and simultaneously surrounded by said fluid concrete while the side walls of said mold prevent the uid concrete from flowing laterally between the core material and the layer of concrete on the bottom wall of Isaid bed and displacing the core material deposited on said layer.
4. Apparatus as defined in claim 3 including:
means for controlling the rate of delivery of said fluid concrete through the outlet of said second hopper so that the fluid concrete flowing off the rear end of the top wall of said mold into contact with the core forming material exerts on said material a vertical pressure which is limited to the weight of said fluid concrete.
5. Apparatus as defined in claim 3 wherein:
said screed comprises a plate having a Ihorizontal bottom surface extending rearwardly from and substantially flush with the bottom edge |of the rear wall of said second hopper,
the spacing between the bottom surface of said screed plate and the top wall of said mold being approximately 1A the distance between the front edge of said screed plate and the open rear end of said mold, and
the rear edge of the top wall `of said mold being positioned rearwardly of the rear edge of said screed plate a distance equal to approximately twice the said spacing between the bottom surface of said screed plate and the top of said mold.
6; Apparatus as defined in claim 3 including:
a finishing screed assembly connected to and movable with said frame rearwardly of said mold, said finishing screed assembly comprising -a transversely extending screed plate slidably supported on the upper edges of the side walls of said bed and having a horizontal bottom surface substantially flush with said upper edges,
a dam member ixed to and extending upwardly from the front edge of ysaid screed plate adapted to catch and carry along the excess uid concrete which lies above the level of the bottom surface of said screed plate, and
mean-s cooperating with said dam for continuously stirring said excess concrete to prevent solidiiication thereof.
7. Apparatus for manufacturing an elongated cored concrete structural member comprising:
a horizontal casting bed having longitudinally extending bottom and side walls,
means for forming a layer of concrete on the bottom wall of said bed,
a frame adapted to be moved longitudinally of said bed,
a plurality of core molds carried by said frame each having longitudinally extending top and side walls, an open bottom and an open rear end, said molds extending downwardly into ysaid bed in transversely spaced relationship with their top walls below the upper edges of the side walls of 'said bed and with the lower edges of their side walls in contact with the layer of concrete Von the bottom wall of said bed, the lower edges of said side walls being inclined inwardly towards one another and so arranged as to cut into said layer of concrete,
a first hopper mounted on said frame adjacent the front ends of said molds having a plurality of outthe open rear ends of said molds, said second hop-- per being adapted to deposit fluid concrete onto the top walls and into the spaces between the side walls of said molds and into the spaces between said molds and the Iside walls of said bed,
a screed for shaping the upper surface of said fluid concrete extending rearwardly from said bottom edge' ofthe rear wall of said second hopper to a point closely adjacent to but forward of the rear edges of the top walls of said molds, and
means for moving said frame longitudinally of said bed in a direction opposite the open rear ends `of Isaid molds continuously during the supply and deposit of the core forming material and uid concrete,
whereby said core material is continuously extruded through the open rear ends of said molds and simultaneously surrounded by said uid concrete while the side walls of said molds prevent the uid concrete from owing laterally between the core material and the layer of concrete on the bottom wall of said bed and displacing the core material deposited on said layer.
References Cited by the Examiner UNlTED STATES PATENTS 857,586 6/1907 Boyle 25-32 940,061 11/1909 Ransone 25--118 965,150 7/1910 Atterbury 25 1,191,731 7/1916 Ransome 25-32 1,274,987 8/1918 Carroll 25 1,684,525 9/1928 Tomarin 264- 256 1,688,422 10/1928 Hyde 264 1,720,855 7/1929 Payne 25-42 1,987,779 6/1935 Knote 264 2,299,070 10/ 1942 Rogers et al. 50--128 2,324,760 7/ 1943 Brulatte 25-32 2,406,025 8/1946 Moor 25-32 2,457,982 1/1949 Deichmann 264- 253 2,618,832 11/1952 Zschokke 25-32 2,648,116 8/ 1953 Mcready. 2,778,088 1/1957 Sterrett 25-154 2,839,812 6/1958 Berliner 25-154 2,948,042 8/1960 Sylvester 25-32 2,956,375 10/1960 Henry et al 50--128 2,970,361 2/1961 Brown 25-99 3,002,249 10/1961 Jackson 25-99 FOREIGN PATENTS 832,870 2/ 1952 Germany. 708,729 5/ 1954 Great Britain. 723,009 2/ 1955 Great Britain.
ROBERT F. WHITE, Primary Examiner.
JACOB NACKENOFF, Examiner.