Concrete extrusion machine and spiral conveyor therefor

A spiral conveyor for a concrete extrusion machine has a first spiral conveyor section with a first external diameter. There is a second spiral conveyor section having a second external diameter which is greater than the first diameter. The second section is spaced apart from the second section. A third spiral conveyor section is between the first section and the second section. The first end of the third section is connected to the first section and the second end is adjacent to the second section. The second spiral conveyor section may be mounted on a hollow shaft of the third section. The second section has two longitudinally divided components, each having a recess therein. Connectors interconnect the two components and a locking device is between the hollow shaft and the second section.

BACKGROUND OF THE INVENTION
 Traveling concrete extrusion machines are typically used for the making
 hollow core concrete slabs. These machines have a hopper which receives
 premixed concrete. The concrete falls into a feed chamber which is mounted
 on a frame. The machines also have a molding chamber where the concrete is
 molded into the profile of the slab. One or more spiral conveyors push the
 concrete from the feed chamber towards the molding chamber and, at the
 same time, propel the machine in the opposite direction. Each of the
 spiral conveyors is rotatable about a non-rotating mandrel shaft. A series
 of mandrels with internal vibrators are connected to the shaft. Similar
 machines are disclosed, for example, in my earlier U.S. Pat. No.
 4,330,242.
 The compression on the concrete in the molding chamber is increased where
 the spiral conveyors have tapered sections such that the flights of each
 conveyor are larger in diameter towards the molding chamber compared with
 flights closer to the feed chamber. This arrangement is shown, for
 example, in my British Patent No. 1,342,601. However, wear is accentuated
 at the end of the spiral conveyor adjacent to the mandrels. This leads to
 a rounding off of the conveyor flights in this location and a
 corresponding reduction in the compression effect otherwise achieved by
 such a tapered spiral conveyor.
 Replacing the spiral conveyors is an expensive proposition since they are
 made of a special high chromium iron alloy. Moreover this involves
 dismantling the extrusion machine with attendant high labor costs and loss
 of production. Accordingly, attempts have been made to provide replaceable
 sections on the spiral conveyors where wear is most extreme. Such an
 arrangement is shown, for example, in Canadian patent 1,205,985 to Kiss.
 This patent shows a conveyor with a replaceable section made in two
 halves. These halves are connected to the main portion of the main auger
 by bolts.
 However, these bolts are often shaken lose by vibrators in the mandrel. The
 lose bolts allow halves of the conveyor to disconnect and can cause damage
 to the machine. Alternatively, the vibrations of the mandrels can cause
 the bolts to become welded to the main auger. Thus the bolts break off
 when attempts are made to loosen them to replace the sections of the
 spiral conveyors.
 It is an object of the invention to provide an improved spiral conveyor for
 a concrete extrusion machine which has a tapered profile, but
 significantly reduces the wear which is normally concentrated at the end
 of the conveyor adjacent the mandrels.
 It is also an object of the invention to provide an improved spiral
 conveyor for a concrete extrusion machine which has a replaceable section
 in a high wear location, but is not adversely affected by vibrations in
 the mandrel or other parts of the machine since it is not connected to the
 main auger by bolts or the like.
 It is hot still further object of the invention to provide an improved
 spiral conveyor with a replaceable section which can be easily removed and
 replaced with a new section without undue labor costs or loss of
 production of the machine.
 SUMMARY OF THE INVENTION
 According to one aspect of the invention, there is provided a spiral
 conveyor for a concrete extrusion machine which has a first spiral
 conveyor section having a first length and a first external diameter. A
 second spiral conveyor section is straight and has a second external
 diameter, which is greater than the first external diameter, and a second
 length. The first section is spaced apart from the second section. A third
 spiral conveyor section is between the first section and the second
 section. The third section is tapered, has a third length, a first end
 being adjacent to the first section and a second end being adjacent to the
 second section. The first section may be straight. The first end has the
 first external diameter and the second end has the second external
 diameter. There is means for mounting the spiral conveyor in the extrusion
 machine.
 According to another aspect of the invention, there is provided a spiral
 conveyor for a concrete extrusion machine. The conveyor has a first spiral
 conveyor section and a shaft extending axially from the first section. A
 second spiral conveyor section is mounted on the shaft. The second section
 has two symmetrical halves. Each half has a semi-cylindrical recess
 therein. Connectors interconnect the two halves and a locking device is
 between the shaft and the second section. The two halves are not connected
 to the mandrel shaft.
 According to a further aspect of the invention, there is provided a
 traveling extrusion machine for forming hollow core concrete sections. The
 machine has a frame and a feed chamber mounted on the frame for receiving
 premixed concrete. A molding chamber is adjacent to the feed chamber.
 There is a mandrel in the molding chamber and a vibrator mounted in the
 mandrel. A rotatable spiral conveyor extends from the feed chamber toward
 the molding chamber. The conveyor has a hallow shaft adjacent the mandrel
 and a section of the spiral conveyor is releasably mounted on the shaft.
 The section of the conveyor includes two halves on opposite sides of the
 shaft. A non-rotation locking device is between the halves and the shaft.
 Connectors interconnect the two halves, the connectors being free of the
 shaft.
 According to a still further aspect of the invention, there is provided a
 traveling extrusion machine for forming hollow core concrete sections. The
 machine has a frame and a feed chamber mounted on the frame for receiving
 premixed concrete. A molding chamber is adjacent to the feed chamber. A
 non-rotatable mandrel shaft extends from the fee chamber to the molding
 chamber. A rotatable spiral conveyor is mounted on the mandrel shaft and
 extends from the feed chamber to the molding chamber. The conveyor has a
 first section within the feed chamber having flights with a first constant
 external diameter. A second section of the conveyor adjacent to the
 molding chamber has flights with a second constant external diameter. The
 second diameter is greater than the first diameter. The second section
 extends along a portion of the conveyor. A third section of the conveyor
 is between the first section and the second section and has flights which
 taper from the first diameter to the second diameter. Preferably the
 second section has a plurality of flights.
 The invention offers significant advantages over the prior art. One aspect
 of the invention provides a spiral conveyor for a concrete extrusion
 machine which is easily replaceable and is not subject to loss of
 components due to vibrations. Moreover, the replaceable section does not
 tend to become welded to the mandrel shaft or the remaining portion of the
 conveyor since bolts can be used to interconnect the two halves of the
 replaceable section, but the bolts do not engage the mandrel shaft or
 other portion of the conveyor. Instead a non-rotation locking device, such
 as a key and a keyway, are used to prevent rotation of the replaceable
 section relative to the main portion of the conveyor. The bolts may become
 frozen due to vibrations, but they can be removed simply by burning off
 the heads of the bolts or nut with a torch. No portion of the bolts or the
 replaceable section remains attached to the other portion of the conveyor.
 Unlike the prior art, spiral conveyors and concrete extrusion machines
 according to another aspect of the invention provide a spiral conveyor
 section adjacent the molding chamber which has a fixed, increased diameter
 over a set distance along the conveyor. This arrangement appreciably
 decreases wear at that point compared with tapered conveyors which
 terminate abruptly adjacent the molding chamber. The larger end of the
 tapered section is where wear typically occurs. The invention extends the
 larger diameter of the conveyor a certain distance adjacent the molding
 chamber. In other words , the conveyor has a larger diameter straight
 section following the tapered section. The larger diameter straight
 section distributes the compression force over a greater area, accordingly
 decreasing wear and increasing the compression effect on the slab being
 formed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Referring to the drawings and first to FIGS. 4-6, these show a traveling
 concrete extrusion machine 20 of the type used to produce a hollow core
 concrete slab 10 as shown in FIG. 6. The machine travels over a stationary
 casting bed 21 in the direction indicated by arrow 57. The machine has a
 frame 24 provided with flanged wheels 25 which ride along parallel rails
 22 of the casting bed.
 The machine has one or more spiral conveyors 27 mounted for rotation in a
 supporting framework 28 which is supported by frame 24. Only one spiral
 conveyor is shown in FIG. 5, and two spiral conveyors are shown in FIG. 4.
 However six spiral conveyors are required to produce the slab 10 shown in
 FIG. 6 which has six hollow cores 11. The spiral conveyors are driven by a
 roller chain train 29 which is operatively coupled to electric motor 30
 mounted on the framework 28. The spiral conveyors rotate about
 non-rotating mandrel shaft 35 shown in FIGS. 1 and 2.
 There is a hopper 32 which receives premixed concrete. The concrete drops
 from the hopper into a feed chamber 38.1. Each spiral conveyor 27 extends
 from the feed chamber 38.1 to molding chamber 39.
 The molding chamber is formed by a pair of vertical side plates 41 which
 are secured to the frame 24 by bolts 42. The side plates have lower edges
 43 which are just clear of the casting bed and serve to restrict lateral
 displacement of the concrete from the molding chamber.
 The molding chamber also has a top plate structure 45 consisting of a pair
 of vibratory plates 46 and 47 disposed in tandem and followed by a
 finishing plate 48. Plate 46 is rectangular in plan and is supported by
 bolts and vibratory dampening blocks 51 mounted on a cross frame structure
 52. The cross frame structure is adjustably mounted on the frame 24 by
 bolts 53. Vibratory plate 46 extends over the spiral conveyor and mandrel
 and has a mechanical vibrator 54 mounted centrally thereon. Vibratory
 plate 47 has a similar vibrator 56 and is mounted on the machine in the
 same manner as vibratory plate 46. Finishing plate 48 is a smooth,
 transversely extending plate mounted in the same manner as the vibratory
 plates. Vibratory plate 46 is positioned a small distance above,
 approximately 1/8 inch above, the elevation of the desired finished
 surface of the slab 10. Vibratory plate 47 is set at the same elevation as
 the finished surface, as is finishing plate 48. Vibrators 54 and 56 are
 chosen and arranged so that the amplitude of vibration of plate 46 is far
 greater than the amplitude of vibration of plate 47.
 Mandrel shaft 35 is connected to a series of mandrels 36, three in this
 example, which are connected in series at the aft end of the mandrel
 shaft. The mandrels are separated from each other and from the mandrel
 shaft by vibration dampening blocks 37 which are formed of a resilient
 material, such as rubber. Each of the mandrels is hollow and houses a
 vibrator mechanism 39.1, only one of which is shown in FIG. 5, operated by
 electric motors inside the mandrels.
 In operation, the machine automatically moves forward in the direction of
 arrow 57 under the pressure of the spiral conveyors against the formed
 concrete in the molding chamber. Passage of the concrete through the
 molding chamber is eased by vibrations set up by the internal vibrators
 and by vibratory plates 46 and 47. Vibrations set up by the internal
 vibrators and vibratory plate 46 normally would cause settlement of the
 slab 10 over the finished cores 11 as the trailing mandrels leave the
 empty cores. However, these large amplitude vibrations are interfered with
 by the vibrations set up by the vibratory plate 47. These vibrations
 further compact the slab, but also serve to dampen the effect of the
 vibrations of the mandrel vibrators 39.1 and vibratory plate 46 so as to
 reduce substantially settling or sagging of concrete as the finishing
 plate 48 passes thereover.
 FIG. 1 shows spiral conveyor 27 in more detail. Conveyor 27 has a first
 spiral conveyor section 100 having a first length L1 and a first external
 diameter d1. There is a second spiral conveyor section 102 having a second
 external diameter d2 which, as seen, is greater than the first external
 diameter. The second section has a second length L2. The first section has
 a plurality of flights 104 which all have the constant external diameter
 d1. Likewise the second section has a plurality of flights 106 which have
 the constant external diameter d2.
 There is a third spiral conveyor section 110 between the first section and
 the second section which has a third length L3. The third section has a
 first end 112 which is connected to the first section 100. In this
 particular embodiment, the first section and the second section are parts
 of a single casting. The first end of the third section has the same
 external diameter d1 as the first section. The third section is tapered
 and flights 114 thereof taper and gradually become larger in diameter
 towards the second section 102. Flights adjacent the second end 118 of the
 third section are equal in diameter to diameter d2.
 Flights of the first section have leading edges 120 and trailing edges 122
 which are both sloped in this example. However the flights in the second
 section of this embodiment have leading edges 124 which are essentially
 perpendicular to axis of rotation 126 of the spiral conveyor. The latter
 configuration helps in compaction of the concrete within the molding
 chamber. The second section 102 of the spiral conveyor is a separate
 component in the embodiment of FIG. 1 and is connected to the third
 section by bolts 130.
 While the embodiment of FIG. 1 does allow the high wear section 102 to be
 replaced, it requires considerable disassembly of machine 20 so that bolts
 130 can be removed and the section replaced. Also the bolts may become
 frozen due to the vibrations discussed above.
 Another embodiment, shown in FIGS. 2 and 3, permits easier replacement of
 section 102.1. Like numbers in this embodiment are used as in FIG. 1 with
 the additional designation "0.1". The second section 102.1 has two
 longitudinally divided components 130.1 and 132. In his particular example
 the two components are symmetrical halves, each half having a
 semi-cylindrical recess 134 or 136 therein. The recesses each receive half
 of hollow shaft 140 which extends from the main portion of the conveyor.
 The shaft may also be regarded as an extension of the main part of the
 conveyor apart from the second section.
 There is a keyway 142 in half 130.1 of section 102.1. Half 132 has a
 similar keyway 144. The keyways extend longitudinally along the halves of
 the section and receive keys 150 and 152 of the hollow shaft respectively.
 In other examples only a single key and keyway may be used. However other
 locking devices could be substituted to prevent relative location between
 section 102.1 and the main portion of the conveyor.
 Each section has a pair of apertures therein, such as apertures 160 and 162
 of half 130.1. Each aperture has a narrower inner portion 164 as shown for
 aperture 160. The apertures 160 and 162 of the two halves are aligned to
 receive bolts 168. Shank 166 of each bolt extends through the narrower
 portions 168 of the apertures, while the wider portions of the apertures
 receive head 170 of each bolt and nut 172. Thus it may be seen that the
 two halves of section 102.1 are connected together by the bolts 168 which
 extend parallel to each other in this embodiment, but are spaced-apart
 from shaft 140. The bolts do not extend into the hollow shaft.
 Accordingly, if the bolts become frozen, they can be removed by simply
 burning off their heads 170 or the nuts 172. The keyway and keys prevent
 relative rotation between the section 102.1 and the main portion of the
 auger, but do not actually connect them together and, accordingly, do not
 inhibit removal of the section from the hollow shaft after the bolts are
 removed from the apertures 160 and 162.
 FIGS. 7 and 7a show a spiral conveyor similar to the spiral conveyor of
 FIG. 2. Conveyor 200 has a section 202 with flights 202.1 of a constant
 diameter D.sub.1. The flights 204.1 of section 204 taper and increase in
 size towards section 206 which has flights 206.1 of a constant diameter
 D.sub.2 greater than section 202. Sections 202, 204 and 206 have lengths
 L4, L5 and L6 respectively. A hollow shaft 208 extends from a one piece
 casting forming sections 204 and 208 in this example. Section 206 is keyed
 onto shaft 208 by a keyway 210. Bolts 209 and 211 connect together two
 halves 205 and 207 of section 206. As seen in FIG. 7, the flights 202.1 of
 section 202 extend radially outwards further from shaft section 202.2 than
 the flights 206.1 of section 206 extend from shaft section 206.2.
 FIG. 8 shows another conveyor 212 with three sections 214, 216 and 218 with
 lengths L7, L8 and L9. The shape is similar to FIG. 7 but the entire
 conveyor is a one piece casting.
 It will be understood by someone skilled in the art that many of the
 details provided above are by way of example only and are not intended to
 limit the scope of the invention which is to be interpreted with reference
 to the following claims: