CA1318757C - Method of making a molded plastic product - Google Patents

Abstract

The molding machine of the present invention comprises a screw extruder for extruding plastic material. A plurality of molds are moved one at a time to the outlet end of the extruder for receiving the plastic material therefrom. The molding is accomplished at low pressures of between 30 p.s.i, and 600 p.s.i. In an alternative form of the invention large irregularly shaped objects may be molded and metal or wooden articles can be embedded within or surrounded by the molded plastic.

Description

1318~ ~

BACKGROUND OF THE INVENTION
This invention relate~ to a method and machine for forming articles from a plastic material. The present invention i particularly adapted for taking waste plastic materials of various heterogeneou~
make-up and processing these materials into products which have properties similar to wood.
One example of a prior process for working up waste plastic material is known by the name ~f the ~Reverzer" proees~, introduced by the Japanese Company Mitsubishi Petrochemical, and mentioned in United gtates Pat~nt 4,187,352. According to thi~
process, sorted or unsorted thermoplastic waste material of, for example, polyethylene, polypropylene, polyvinylchloride or mixture~ thereof, i~ comminuted and the particulats material is subsequently stored in a storage space. The particulate material is dried to a certain extent, u~ing the heat released during the communition of the waste material. From the storage space, the particulate waste material is supplied to the "Reverzer" unit, which in essence is a melting unit, comprising a hopper in which the matarial i8 softened, and a mixer comprising a screw member, in which the material i8 also fluidized. The fluid material is then in~ected under very high pressure into a closed mold and thus molded. The mold~ are then transported to a cooling space, and cooled by being sprayed with water. The mold3 are then opened ,' ~

~ 31~5~

and the molded product is removed. The re~ulting products may ha~e the form of tapered beams, frames, V-beams, etc., depending upon the mold being used. In this prior process, a very high pressure is built up in the mixing and fluidization ~tage of the apparatus used, under the influence of which, as stated, the - fluid material is injected into a special pressure resistant mold Rlobbie Patent 4,187,352, discloses a method for working up thermoplastic plastic synthetic material into shaped particles in which specially adapted pressure resi6tant apparatus is unnecessary, but commercially a~ailable non-pressure resistant apparatus and dies or molds can be used.
The ~lobbie patent discloses apparatus in which the synthetic material is subjected to a mixing operation in a housing comprising a screw member, and is fluidized, molded, cooled in the mold, and removed from the mold. The synthetic material is supplied ~o an extruder without a screen pack and without an extrusion no~zle. The mold into which it is extruded is open at both ends so that the fluid is not under pressure within the mold. Moiding pressure is obtained by mixing with the particulate synthetic material a blowing agent, the threshold temperature of which is exceeded at the temperature occurring in the extruder. The blowing agent causes gas to be propagated so as to increase the pressure wi~hin the mold, there~y causing the plastic material to assume the shape of the mold.
Therefore, a primary object of t~.e present invention is the prov-sion of an improved machine and method for reprocessing waste polymers to c-eate a molded p_oduct unàer low pressure.

13~7~7 A fur~her ob~ect of the present invention is the provision of a machine and process which utilizes low pressure so as to permit the use of an insxpensive mold, but at the same time using a pressure which is higher than that shown in the Klobbie reference referred to above.
A further object of the present invention is the provision of a machine for molding waste polymers which creates a molding pressure within the extruder by use of a nozzle and an optional screen pack~
A further object of the present invention is the provision of an improved machine for processing waste polymers wherein the polymers can be contaminated with various impurities.
A fu_ther object of the present invention is the provision of a machine for processing waste polymers which includes a closure device for closing off the ends of the molds during the molding process.
A further object of the present invention is the provision of a machine for molding waste polymers at a low pressure, but which provides sufficient molding pressure without the need of a blowing agent as shown in the Klobbie patent.
A further object of the present invention is the provision of a machine which includes an automatic fill sensiny device which senses when the mold is full and causes it to be indexed away from ~he extruder.
A further object of the present invention is the p-ovision of a machine for processing was~e polymers which utilizes a hecting band ~o cause ~he waste polymexs ~o achieve 2 -^luid s~a~e fox extruding.

1318 r7 ~ 7 A further object of the present invention is the provision of a method of molding large and irregularly shaped objects at pressure of from 100 psi squar~ to 600 psi.
. .
A further object of the present invention is the provision of a method of molding objects embedded withln the plastic .. . . .
molding material at relatively low pressure from 100 psi to 600 psi.
A further object of the present invention is the provision of a machine which i5 Pconomical to manufacture, durable in use and efficient in operation.

SUM~.ARY OF THE INVENTION
The present invention pro~ides a machine for forming products out of waste polymer materials by utilizing a molding pressure substantially greater than that shown in the Klobbie patent referred to a~ove, but substantially less than the high pressure molding referred to in the ~Reverzer~ process referred to above. As a result, the advantages of molding with a relatively low pressure, i.e., the inexpensive equipment and molds are achieved with the present invention, while at the same time eliminating the disadvantages encountered with the Klobbie proces 5 .
The present invention utilizes an extruder having an optional screen pack and nozzle head therein. A heater b2nd surrounds the nozzle so as to supply heat to the plastic material before it is extruded. The use of the screen pack and the nozzle c_eate a higher pressure for the plastic mate~ial than the ~ 3~g75~
pressure obtained in the Klobbie patent. Pressures in the mold need to be sufficiently high to give good quality moldings. For simple moldings, lower pressures give adequate quality, but if the mold has any detail to be shown, then higher pressures are required. Typically the lowest pressure which would produce acceptable moldings would be approximately 30 psi and the highest pressure would be approximately 600 psi. The preferred pressure is dependent upon the nature of the mold.

The plastic materials which may be molded with the present invention incl~de a variety of materials such as low, medium, or high density polyethylene; polypropylene; polystyrene; ABS;
polyamide; and polyester. The input materials can be mixed and can have low quality with a large number of impurities therein such 2S ground particles of metal.
The present in~ention utilizes a mold holder which holds a plurality of molds and which indexes the molds one zt a time, first to a fill s~ation where the molds receive the pl2stic material from the extruder, and then to a second sta~ion wherein the ends of the mold are closed and the molded material is permitted to cool and harden while under pressure. Between the fill station and the second station, a trimming apparatus is provided for trimming any excess material from the ends of the mold prior to the time that the ends of the mold are closed at the second station.
After filling the machine rotates the mold holder to bring an empty mold to the filling station. The mold is filled, and a sensing devlce zt the end of the mold senses when the mold has been filled.
_ -6-13~87~7 The ~ull mold is taken to a holding station where it i8 held closed. Closure at the fill orifice i~ maintained by a pressure piston which presses the fill opening of the mold against a flat metal plate. At the efflux orifice at the other end of the mold, closure is maintained by the pressure pi~ton pressing ~gainst the end plate of the mold. This piston is held in place by a pneumatic cylinder which ~lso generates the pressure to give closure at the inlet orifice.
After the mold has been filled, the plastic that has issued from the mold must be trimmed flush with the end face of the mold, thus allowing a good seal by the mold closing device. ~his operation is performed by a self-positioning cutter located between the fill station and the holding statio~.
The nozzle has two functions. It generates a pressure in the extruder and insures complete mixing of the various components of the input material. It also enables the molds to be filled from a relatively small orifice so zs to allow such molds to be of relati~ely small cross-sectionzl are2 when compared with the ex_ruder barrel diameter.
Nozzle heater bands are thermostatically controlled so as to hold the extrudant at a fairly constan~ temperature and so as to give the desired flow properties.
A modified form of the invention utilizes an extruder molding machine without the carousel described above. Instead, a ram is used to press a mold into communication with the outlet opening of the ext_uder. The extruded plastic is then forced into the mold znd ills the mold. It has been found tha- lz-ye znd 131~73~
irregularly shaped molds can be utilized with this m~thod while at the same time usin~ molding pressures that are in the range of 100 to 600 pounds p~r square inch, and are in the preferred range of 300 to 600 pounds per square inch. The temperature may be adjusted to the particular composition of material being molded, but preferably it should be in the range of 350 degrees Fahrenheit to 600 degrees Fahrenheit. The molding of a mixture of polyester, polye~hylene, polypropylene, modified polyethylenes, and other impurities such as metal provides a superior result from that obtained with pure homogeneous plastics. The pure plastics tend to "sin~" within the mold. That is, they te~d to shrink upon curing so that they are substantially smaller than the shape of the mold. However, the combination of waste plastics utilized in the present invention does not experience shrinkage or "sin~;ing" to the extent tha~ is encountered with pure plastics.
In yet another modified form of the p-esent invention, solid o~jects can be molded and embedded within the plastic materizl.
This is accomplished by suspending the object withir. the mold Pnd forcing the molten plastic into the mold around the object. In this manner, it is possible to e~ed metal and/or wooden objects wi~hin the plastic. For example, it is possible to embed a metal rod within the plastic, or it is possible to embed z wooden object such 2S a _ailroad tie within the plastic. All of this is accomplished at consider~bly lower pressur~s ~han heretofore ~nown in the 2rt.
BRTE~ D~SCRI?TION O~ TH~ 3R~-h-TNES
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1318rl~3~
Figure 1 is a side elevational Yiew of the present invention showing portions thereof in ~ection.
Figure 2 is a top plan ~iew of the right-hand portion of the device shown in Figure 1.
Figure 3 is a sectional view taken along l~ne 3-3 of Figure

2.
Figure 4 is a sectional view taken along line 4-4 of Figure

3.
Figure i is a sectional view taken ~long line 5-5 of Figure Figure 6 is a sectional vi~w taken along line 6-6 of Figure 3.
- Figure 7 is a perspective view of modified form of the present invention.
Fiyure 8 is a plan view taken along line 8-8 of Figure 7.
Figure 9 is an exploded perspective view of a mold and molded object which can be produced on the deYice of Figure 7.
Figure 10 is a sectional view ta~en along line 10-10 of figure 9.
Figure 11 is an elevational view of a different mold which can be used with the device of Figure 7.
Figure 12 is a perspective exploded view of the mold and molded object shown in ~igure 11.
~ igure 13 is a sectional view taken along line 13-13 of Fiyure 11.
Figure 14 is a sectional view of a furthe- mol~1 which can be utilized wi~h the device of Fi~-e 7.

13~737 Figure 1~ is a sectional ~iew take~ along line 15-15 of Fiyure 14.
Figure 16 is a longitudinal sectional view of an object molded with ~he mold of Figure 14.
DE~AILED DESCRIPTION OF THE PREFERRED EMBODI~ENT
Referring to the drawings, the numeral 10 generally designates the machine of the present invention. ~achine 10 includes a screw extruding machine 12. Extruding machine 12 includes an input hopper 14 for adding the comminuted plastic waste materials which will be extruded through the machine.
Extruder 12 includes an extruding barrel 16 (Figure 4) having a screw 18 therein for driving the plastic material toward the discharge end of the barrel. At the discharge end of the barrel is a noæzle 20 havin~ an ex~rusion aperture 22 therein.
The nozzle has the function of generatiny a pressure in the extruder so as to insure complete mixing of the ~arious components of the input material. ~urthermore, the nozzle enables the molds to be filled from a relati~ely small orifice so as to 2110w the molds to be of a relatively small cross-sectional area when compared with the extruder barrel diameter.
A nozzle heater band 34 surrounds nozzle 20 and is adapted to permit thermostatic con~rol of the temperature of the extruded material, thereby maintaining the material at a cons a~
temperature to obtain the desired flow properties at the nozzle head.
The nozzle is bolted or oth~rwise operati~ely secured to a lzrge ci-cular fixed plate 36 which -emainC stztion2ry wi~h respect to the extruder machine 12. Al~o attached to the extruding machine 12 is a rectangular tank 38 having side walls 40, 42, end walls 44, 46, and a ~ottom wall 48. Tank 38 is adapted to hold a water bath or other cooling fluid 50 therein.
Mounted in the bottom of tank 38 are a pair of upstanding pedestals 52, 54 which include bearings 56, 58 at their upper ends for rotatably receiving a tubular shaft 60 therein. Shaft 60 extends rotstably in bearings 56, 58 and also extends rotatably ~hrough a sleeve 62 centrally located in circular plat 36.
Mounted on the outside of shaf~ 60 are a pair of spaced apart carousel plates 64, 66. Each plate 64, 66 includes a cylindrical sleeve 68 having a bushing 70 therein. Threaded within sleeves 68 are tightening rods 72 which are adapted to tighten against bushings 70 so as to clamp plates 64, 66 against sliding movement along shaft 70. The distance be~ween plates 64, 66 may be adjusted by loosening rods 72 and by sliding the plates 64, 66 to the desired relative spaced apart positions.
Each plate 64, 66 includes a plurality of circular o?eninss 74 therein. Mounted within openings 74 and spanning the cistance between carousel plates 64, 66 are a plurality of elongated molds 76. Each mold includes a firs~ open end 78 and a second closed end 80. ~itted over end 80 is a closure plate 82 (Figure 4) having an efflux orifice 84 therein for penmitting g2ses to escape as the mold is being filled. Closure plate 82 is circular and is retentively fit~ed within the circular opening 74 of ca-ousel pl~e 66. Open end 78 of mold 76 is _i~ed 2c~ins l3l~7~7 circular plate 36. Welded oz o~herwise ~ecured to the outer surface of mold 76 is a circular plate 84 which is sized to fit retentively within the opening 74 of carousel plate 64. Thus molds ?6 are suspended between carousel plates 64, 66 by means of closure plate 74 and circular plate B4 being fitted within the openings 74 of carousel plates 64, 66. The particular means for holding circular plates 82, 84 in openings 74 may vary, and may include clamps, set screws or other means ~o ~s to attach the molds to the carousel plates 64, 66.
Moun~ed to the end of shaft 60 is a pulley 86. A drive motor 8~ includes an output shaft 90 having a pulley 92 thereon.
A belt 94 is trained around pulley 92 and pulley 86 so as to pxo~ide d~iving connection between motor 88 and shaft 60, thereby providing means for rotating the shaft 60 and the carousel plates 64, 66. A con~rol box 95 is adapted to control motor 88 so 25 to cause the ca~ousel plates 64, 66 to be moved in increments one a.
a time which will cause the ~arious molds to mo~e one at a time from a filling station designated ~y the numeral 96 in ~igure 3 to a holding or hardening station 98, and thence to periodic other stations 100-110 as shown in ~igure 3.
Nounted for sliding movement on the upper edges of side walls 40, 42 of tank 38 is a sliding frame 112 ha~ing a pair of cross frame members 114 spanning the distance between side walls 40, 42. Fixed to c~oss frame mem~ers 114 is a fill sensing assembly 116 which includes a fill sensing box 118 positioned in facing relationship to carousel plaLe 66 at the fill station 9D.
Fill sensing ~ox 118 ls s~o~n in sec~ion in Fig~-e 4 and in~l~des --_2--7~7 an elongated arm or blsde 12~ which is piYoted at 122. On the lower end of arm 120 is a balance weight 124 which fits in facing relationship to aperture 83 in closure plate 82 of mold 76. The upper end of arm 120 is pro~ided with a magnet 126 which is normally in engagement with a switching device 128. In their normal position, magnetic reed switch 128 controls motor 88 so that there is no rotational movement of the carousel plates when the mold 76 is at the fill station 96.
Upon actuation of the screw extruding machine, plastic material is extruded outwardly through extrusion aperture 22 into mold 76. As the plastic material begins filling the mold 76, it ultimately begins issuing outwardly throush fill sensing aper~u~e 83. When this happens, counterbalance 124 is moved to the right as viewed in Figure 4, thereby causing magnet 126 to brea~
contac~ with magnetic reed switch 128. When contact is broker between magnet 126 and magnetic reed switch 128, the extruder is stopped and motor 88 causes the carousel plates 64, 66 to be indexed and moved so that the mold 76 progresses fro~ the fill station 96 to the h2rdening station 98.
Positioned between fill station 96 and hardening station 98 is a sprue cutting device 130 shown in Figures 2, 3 and 5. Sprue cutting device 130 includes a base frame 132 which is fixed to sliding frame 12 and which extends downwardly therefrom. At the lower end of base frame 132 is pivoted a ~nife arm 134 ha~ins a ~;nife blade 136 thereon. A hydraulic o. pneumatic cylinder 138 is connected at one of its ends to base frame 132 and at the other o_ its ends ~o knife arm 13A. Cylinde~ 138 main_ains kni_e 13~r~17 blade 136 in facing relationship to the outer surface of closure plste 82, and is adapted to trim any resin that has issued from the orifice 83 of the mold. As the mold moves from the fill station 96 to the hardening station 98, the blade 136 wipe~ along the surface of closure plate 82 and trims the mold flush with ~he end face.
Mounted at the hardening station 98 is a mold closing device 140. Device 140 includes a cylinder 142 which is rigidly mounted with respect to slidins frame 112. Cylinder 142 includes a rod 144 having at its outer end a circular pad 146 adapted to fit in sealing engagement over fill sensing aperture 83. When the mold 76 reaches the hardening station 98 it stops, and cylinder 142 is extend~d so ~hat pad 146 fits in sealing engagement over aperture 83. The pad 146 also exerts axial pressure on mold 76 so 25 to cause the open end 78 of mold 76 to be tightly fi~ted against ~he surface of fixed plate 36. Thus, both ends of mold 76 are closed by virtue of the pneumatic cylinder 142 during the time that the mold is at hzrdening station 98.
At the szme time, the mold immediately following mold 76 is now at the fill station and is being filled. With the next indexing of the carousel plates, the second mold comes to the hardening station and the first mold progresses downwardly toward the bath 50 ~ith tan~ 38. By this time the plzstic materizl hzs ha_dened within mold 76 and does no -ecui~e closure at the opposite ends of the mold 76.
After the molds have been more thoroughly cooled by s~1~jec_ing ~hem _o ~he cooling ~a.h 53, ~hey czn be em?~ied cnd used 2g~in fc- the Corming of addi~icnal p-oducts.

~3~ 7 The present invention thus permitz the molds to be fille~ at a relatively low pressure, so as to eliminate the need for more expensive molds used in the high pressure molding ~echniques.
However, the present invention permits the molds to be filled under somewhat greater pressure than that achieved with the ~lobbie patent discussed abov~. There is therefore no need for blowing agent to provide the molding pressure within the mold.
The fill sensing device provides an improved method for determining when the mold is full and automatically signaling the machine to index the mold to the next station. The trimming blade and apparatus 130 trims the end of the mold au~omatically so as to insure a tight seal when the m~ld is positioned in the hardening station. At the hardening station, the mold is closed at both ends so as to permit the molded material to completely harden with both ends of the mold closed.
Referring to Figure 7 the numeral 200 generally designates a screw extrusion machine similzr to screw extruding machine 12.
~achine 200 includes a control console ~02, an inpu' hop?e_ 20~
fo- aàding the comminuted plastic ~-aste materials wh_ch will be ex~ruded through the machine, and a screw eY.truder designated generally by the 206. xtruder 206 includes a plurality of heating elements 208 around the outer surface thereof which c2n be controlled by console 202 so as to provide the desired ~emperature fo, molding va-ious types of plastic comminuted materials. Extruder 206 includes an extrusion die 210 through which the plastic material is forced for molding.

13~7~7 Supported in paced ~part rel~tion to extruder die 21~ is a hydraulic cylinder 212 ha~ing a ram 214 mounted therein for telescopic movement in response to actuation of cylinder 2~2.
Ram 214 is mounted for movement along a line which is ubstan~ially registered with the sxis of extrusion die 210.
Cylinder 212 is held in fixed relation to extrusion die 210 by a ~upport frame 215.
Mounted between extrusion die 210 and ram 214 are a cylindrical spacer block 216 and an irregularly shaped mold 218.
Mold 218 is formed into a shape for the frame of a bench which is designated by the molded bench frame 220 (Figure 9) having a pair of spaced apart legs 22~, 224, an upstanding back 228 and a horizontal support surface 226. Frame 218 includes an L-shaped brac~et 230 which is adapted to ,it against spacer block 216 so that, when extended, ram 214 exerts a force directly through spacer block 216, L-shaped bracket 230, and mold 218 to the die 210 of the extruder 206.
~lold 218 includes a hollow mold section 232 h2ving an inlet opening 234 at one end thereof. A cover plate 236 is adap.ed ~o fit in co~ering relation over hollow frame 232 to provide a complete enclosure therein. Clamps or other securing means can be used to secure ~over plate 236 tightly in covering relation over the open end of hollow frame 232. A plurality of ~noc~ou_ bolts 238 are slidably fitted within hollow frame 232 for facilita~ing the removal of the molded bench frame zfter the molding is complete.

13187~7 In order to mold the bench frame 220 it is necessary to place the mold 218 between the spacer block 216 and ~he die 210.
The inlet opening 234 of frame 21R is placed i.~ registered alignme~t ~ith die 210 so as ~o permit the mclten plastic material issuing from die 210 to enter the interior of mold 218.
Mold 218 is held in place by extending the cylinder 212 and the ram 214 so as to press spacer block 216 against frame 21B.
Comminuted waste plastic material is then placed withi,l hopper 204 and the screw extrusion machine 200 is actuated and controlled by console 202. The com.ninuted waste plastic materials may be those which are con~entionally produced by vzrious plastic was~e materials such zs beverage containers. I~
mey include polyester, polyethylene, polypropylene, and modif ed polyethylenes. It also may include other foreign waste materials such as metal coming from the bottle caps of beverage containe-s.
~7hile it is not necessary that all of the abo~e materials be included in the co.~minuted material, it is preferable that at least two of the above mate-ials be in~luded.
The ex~ruder is used to heat and a?ply p-essure to the conminuted material and thereby produce a molten plastic ma~e_izl which is forced outwardly throuyh the die 210. The pressure applied by the eY.truder may vary from as low as 100 lbs. per sq.
inch to as high zs 600 lbs. per sq. inch. Prefe-ably the pressure should be approximately 300 ~o 600 lbs. per s~. inch.
The temperature also can be adjusted to produce the best results with the particulzr combination of material being molded. ~he mold ng tem?e-2~u-e should t'2ry -om 2??-oY m~ely ~;0 àes_ees ~zh-enhe~ ~o z?p~o~im2~e'y ~00 deg-ees ~hrenhe_ .

i~l87~7 The extruder i~ then actuated so as to force the molding ma~erial into the mold 218. The desired molding pre~sure within mold 218 can be achieved by varying ~he pressure ~ith ~hich ram 214 holds the mold 218 against the die 21~. Exerting a lesser force will result in the mold filling with a lesser pressure and exexting a greater ~orce with the ram 214 will result in the mold 218 being filled to a greater molding pressure.
Aftex mold 218 is full the mold is removed and the material - therein permitted to cure and harden. ~nockout bolts 238 are then used to remove the molded object 220.

The present in~ention permits the molding of large and complicated irregular objects at a very low molding pressure.
Prior ~o the present invention such large and complicated objects required molding at very high pressures. However, by utilizing the combination o. molding materials and by utilizing the extruding machine 200 and the ram 212 it is possible to mold objects at very low pressures ranging from 100 p.s.i. to 600 p.s .i.
Refer~in~ to figures 11-13 a furthe~ type of mold 2~0 is shown in use with the extruding machine 200. Mold 240 can be used to mold an foreign object such as metal bar 242 within a plastic molded body 244. Mold 240 comprises two mold halves 246, 248 each havin~ semi-circular openinss 250 ad2p~ed .o fi. c~ound and receive metal bar 242. Mold half 248 includes a flat lange 252 which is adapted to fi~ agains~ the die 210. ~lange 252 includes a molding inlet opening 254 which permits the molàing com~ound (desicna_ec ~y ;he numer21 256 in ~ig~-e 13) ~o er.~e=
from die 210 into the mold 240.
-'8-~31$7~7 The-molding process is e~sentially the same as for the device shown in Figures 8-10. The material is forced through dle 210 into the mold at a pressure of from 100 to 600 lbs. per sq.
inch and at a temperature of from 350 degrees Fahrenheit to 600 degrees Fahrenheit. The pressure within mold 240 is controlled by the force exerted by c~linder 212 and ram 214. It has herefore been un~nown in the art to be able to mold an object such as body 244 with a foreign object such as bar 242 embedded therein at pressures as low as 100 to 600 lbs. per sq. inch.
Referring to Figures 14-16, a large wooden object such as railroad tie 258 is shown molded within a plastic material designated by the numeral 260 in Figure 16. This constxuction can be ~aluable for items such as railroad ~ies, poles, pilings, posts, and the like which are exposed to the elements and which can rot and dete-iorate with time. By molding the railroad tie 258 wi~hin a pl~stic 260 it is possible to preserve the railroad tie over much longer periods of time 'hen presently possible.
~hile me~hods for e~:t-uding small wooden objec~s ~ithin plas~ic are known in the art, it is has not been };nown how to mold lzrge objects such as railroad tie 258 within plastic. The p-esent invention ma~es such molding possible.
Referring to Fi~ure 14, a mold 262 comprising mold hal~es 264, 266 is ?laced between the extruder die 210 and ~he s?acer bloc~ 216 of cylinder 212 and ram 214 (not sho~-n). ~'ithin the mold hal~es 264, 266 is the railroad tie 258. A plurali~y o spacer pegs 268 ex~end from railroad tie 258 to the ~alls of ~he mold 262 as is ill~s.~a_ed in ~isures 14 and lS. Pess 268 2-e ~3l ~73~

: preferably made rom plastic so that they will ultimately become part of the plastic material 260 surrounding railroad tie 258.
The extruder 200 is then actuated to force the molten plastic into the mold 262 through an inlet orifice 270. The pressure within the mold 262 is controlled by the force with which the cylinder 212 and the ram 214 exert against the mold 262. Preferably this pressure should be between 300 p.s.i. and 600 p.s.i., and the moldin~ tempera~ure should be maintained between 350 degrees Fa~renheit and 600 degrees Fahrenheit.
~ he molding compound fills ~he space within the molds and surrounds the railroad tie 258. ~he plastic pegs 268 pa-tially melt and form integrally with molding plastic so 25 to create the plastic material 260 shown in Figure 16. The railroad tie 258 is thus embedded within the plastic through a molding process.
While the process described abot~e is a manual process for molding railroad tie 258 in plastic, it is also possible to fully automate the molding process by utilizing the carousel molding machine 10 ~ith a plu-ality of elonGate~ molds containing railroad ~ies. In such applications the mold fill ng hole 270 is at the end of the mold so 2S to fit against nozzle opening 22.
Also the opposite end of the mold is open and is pressed against plata 82 (~ig. 4) for molding in accordance with the method set forth for the de~ice of Figures 1-6.
Thus, it can be seen that the de~ice accomplishes at lezst all o~ its stated objecti~es.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1.

A method for molding plastic objects comprising:
grinding a combination of waste plastic materials into a comminuted mixture, said combination of plastic materials comprising at least two materials selected from a group of materials consisting essentially of polyester, polyethylene, polypropylene, modified polyethylenes, and metal;
feeding said mixture into the hopper of an auger extruder capable of applying heat and pressure to said mixture;
using said auger extruder to heat said mixture to a temperature of approximately 350 degrees - 600 degrees Fahrenheit whereby said mixture will melt and to force said molten mixture outwardly through a die opening under a pressure of from approximately 100 lbs. per sq. inch to 600 lbs. per sq.
inch;
holding the inlet opening of a mold in tightly sealed relationship over said die opening so as to receive said molten mixture issuing from said die opening, said mold having an enclosed cavity in communication with said inlet opening for receiving said molten mixture;
continuing to use said extruder to force said molten mixture through said die opening and said inlet opening into said enclosed cavity of said mold until said mold is completely filled with said molten mixture at a pressure of from 100 to 600 p.s.i.;

removing said mold from said extruder after said cavity is filled;
permitting said mixture within said mold to cool and harden;
removing said hardened mixture from said mold.
2.
A method according to claim 1 and further comprising maintaining said mixture free from a blowing agent other than the air which naturally forms in said mixture while passing through said extruder.
3.
A method according to claim 1 comprising using a complex mold having an irregularly shaped cavity therein, said mold being comprised of at least two separate parts, and separating said mold parts from one another in order to reprove said hardened mixture from said mold.
4.
A method according to claim 1 comprising using a mold having a foreign object within said cavity whereby said molten mixture will surround and embed said foreign object therein when said molten mixture fills said cavity and said foreign object will be embedded within said hardened mixtures.
5.
A method according to claim 4 comprising holding said foreign object in spaced relationship to said mold during the time that said extruder forces said molten mixture into said cavity whereby said molten mixture will completely surround and enclose said foreign object.