GB2067165A - Additive metering device for plastics moulding process - Google Patents

Abstract

An additive metering device 20 for metering a predetermined quantity of additive material, such as pelletized colour concentrates and/or pelletized additives to a material conveyed by a loader system 10 from the respective storage bins 12, 14 to a plastics moulding machine 18, said metering device 20 having a metering shaft 24 rotatable in a casing 22 having an inlet and an outlet and said shaft 24 having a cavity 52 of which a portion 58 is received within the casing 22, the volume of the cavity within the casing 22 being adjustable so as to adjust the quantity of additive material discharged from the device 20 during each rotation of the shaft 24. <IMAGE>

Description

SPECIFICATION Additive metering device for plastics moulding process This invention relates to an additive metering device for use in a plastics moulding process.

In the plastics industry it is common practice to transport finely divided, granular or pulverant material from a storage bin, through a feed pipe to a material receiving hopper assembly by creating a vacuum to draw the material from the storage bin into the feed pipe. The material in the receiving hopper assembly is used to charge a plastics moulding machine.

In many instances, it is desirable to add a predetermined quantity of pelletized colour concentrates or other pelletized additives, such as stabilizers or plasticizers, to the conveyed material prior to charging of a plastics moulding machine therewith. A common arrangement used heretofore for adding pelletized colourant consisted of a screw conveyor or auger feed to convey the colourant from an additive storage bin to a main storage bin or to a common intermixer assembly.Such screw conveyors have generally proved satisfactory, however certain deficiencies therewith have been observed, for example: pelletized colourant can become lodged intermediate the inner periphery of the cylinder and the outer periphery of the auger thus resulting in increased wear with respect to the auger and cylinder, strain on the motor utilized to drive the auger and a decrease in colour consistency; the let down ratio between the colourant and the virgin is limited because the only adjustment to the auger capacity is by varying the rotative speed thereof and is further limited because of a lessening in metering accuracy of an auger feed at higher rotative speeds; and the cleaning of an auger feed arrangement during changeover of colourant or other additive concentrates is time consuming.In as much as in many instances an exact quantity of additive is important for colour uniformity and/or the uniformity of physical characteristics of a given run of moulded articles, even slight variations in the amount of additive conveyed to the main material storage bin of a common intermixer assembly could produce a substantial adverse effect on product uniformity.

Various arrangements have been conceived heretofore for curing or alleviating the deficiencies indicated hereinabove; however, none of these other arrangements alleviate, in an efficient manner and at a reasonable expense, all of the above-mentioned deficiencies. For example, in our U.S. Patent No. 3,954,303, there is disclosed an apparatus which ulitizes a flexible sleeve surrounding the auger section to alleviate the lodging of the pellets between the auger and sleeve periphery; however, this arrangement does not alleviate the other basic drawbacks of an auger feed arrangement.Still further, other system users have abandoned the auger feed arrangement and have used central colour blenders in an attempt to overcome the deficiencies mentioned above; however, central colour blenders may operationally result in segregation of the colour or additive pellets from the virgin material due to the difference in pellet size and material travel distance and also necessitate time consuming clean up procedures during colourant or additive changeover.

According to the present invention there is provided a metering device for metering particulate additive material to a moulding material prior to the charging of a plastics moulding apparatus, comprising a body member having an elongated hollow portion with vertically spaced openings extending from oppositely disposed portions of said hollow portion and longitudinally with respect to said hollow portion; an elongated selective rotatable member closely longitudinally received within said hollow portion and having an elongated cavity therein, said cavity having at least a portion thereof rotatably moveable into and out of indexing relationship with said spaced openings for the metering of such additive during the rotation of said rotatable member; and adjusting means having at least a portion thereof received within said cavity for selectively varying the longitudinal extent of said portion of said cavity.

The metering device of the present invention offers substantially greater accuracy over a larger range of feed capacities than an auger feed arrangement. Furthermore, because the capacity of the metering device of the present invention may be varied by selectively varying the volume of the feed cavity and/or the rotative speed of the shaft, a greater range of let down ratio of colourant to virgin is possible. Still further, the body member and rotatable member arrangement of the present invention permits shearing of the additive pellets during rotation thereof, thus preventing binding, inefficiencies and potential motor damage. In addition, the body member and rotatable member may be formed of high carbon steel and/or surfaced hardened to economically and efficiently withstand the abrasion and shear strength of the additive pellets.

Furthermore, the metering device of the present invention is easily and rapidly cleaned during colourant or additive changeover.

Two embodiments of the present invention will now be described, by way of examples, with reference to the accompanying drawings, in which: Figure 1 is a side elevational view of a portion of a plastics moulding machine loading assembly which incorporates therewithin an additive metering assembly according to one embodiment of the present invention, Figure 2 is an elevational view taken on lines 2-2 of Fig. 1 in the region of the additive metering device illustrated therein, Figure 3 is a longitudinal cross-sectional view taken on line 3-3 of Fig. 4 illustrating a portion of the metering shaft and meter housing of the additive metering device of the present invention and wherein the shaft is not shown in cross-section, Figure 4 is a transverse cross-sectional view taken on line 4-4 of Fig. 3, Figure 5 is a transverse cross-sectional view taken on line 5-5 of Fig. 3 and illustrating the meter housing only, Figure 6 is a side elevational view of a rotatable end gate used in conjunction with the metering shaft illustrated in Figs. 3 and 4, Figure 7 is an end view of the end gate as viewed on line 7-7 of Fig. 6; and Figure 8 is a perspective view, partially in section, of another embodiment of an additive metering device according to the present invention and of the type which may be used with the plastics moulding machine loading assembly illustrated in Fig. 1.

Figs. 1 and 2 illustrate a portion of a loader assembly 10 incorporating therewithin an additive metering device according-to the present invention and the assembly 10 comprises a main material hopper 12; an additive hopper 14 located transversely adjacent a lower end portion of hopper 12; a mixer assembly 16 located below the adjacent hoppers 12 and 14; and an additive metering device 20 according to the present invention which provides metered communication between the additive hopper 14 and the mixer assembly 16. Loader assembly 10 is of a type for transporting material to a plastics processing machine and, in the particular assembly illustrated in Figs. 1 and 2, is utilized for transporting virgin raw material for plastics moulding processes from the respective storage bins therefore (not shown) to a plastics moulding machine which is schematically illustrated at 18.

In as much as the invention herein is primarily directed to the additive metering ievice 20 and the structure, co-operation and operation of the other elements of loader assembly 10 are generally well known in the art, a detailed description of such other elements is not necessary to one skilled in the art for a full understanding of the invention herein and will not be set forth hereinafter except when required to further describe metering assembly 20. For further description of a loader assembly such as assembly 10, reference is hereby made to the general description in our U.S. Patent No. 3,954,303.

Additive hopper 14 provides storage means for pelletized colour concentrates or other pellet additives, such as stabilizers or plasticizers, which are to be metered therefrom by the metering device 20 into the mixer assembly 16 wherein they will be mixed with the material from the main material hopper 12 for subsequent discharge into the plaastics moulding machine 18. Transporting additive material to the hopper 14 is accomplished by any suitable means; for example, by gravity flow or by vacuum loading in a manner as is illustrated in U.S. Patent No. 3,954,303.

Metering device 20 comprises an elongated housing 22; an elongated metering shaft 24 which extends through the housing 22 and has respective axial end portions thereof extending longitudinally from adjacent longitudinal ends of the housing 22; and a selectively energizeable drive motor 26 for effecting the rotation of the shaft 24 about the longitudinal axis X-X thereof. For the purposes of description hereinbefore and hereinafter, and with reference to the drawings: axially and longitudinally shall be with reference to the longitudinal extent of axis X-X; forwardly and rearwardly and forward and rearward shall refer respectively to away from and towards the drive motor 26; and upwardly and downwardly and upper and lower shall refer respectively to the top and bottom of the various elements of metering assembly 20 as viewed in the drawings.

The housing 22 comprises an additive receiving portion 28 which extends longitudinally between forward and rear end walls 30 and 32, respectively. Rear end wall 32 has an opening (not shown) therethrough which is coaxial with respect to axis X-X and is of a diameter substantially equal to the diameter of the shaft 24 for the receipt of the rear end portion of the shaft 24 therethrough. The forward end wall 30 includes a longitudinally stepped coaxial opening 34 therethrough which receives the forward end portion of meter shaft 24 therethrough. As illustrated, opening 34 consists of a rear portion 36 having a diameter thereof substantially equal to the diameter of the shaft 24 and a forward portion 38 having a diameter thereof larger than the diameter of rear portion 36.

The additive receiving portion 28 of the housing 22 includes a vertical opening 40 therethrough which extends continuously longitudinally between end walls 30 and 32.

As best illustrated in Fig. 5, opening 40 comprises an upper downwardly tapering portion 42; a vertically intermediate portion 44 of a circular cross-section having a diameter thereof substantially equal to the diameter of the metering shaft 24 and which is in open communication with portion 42 adjacent the lower end of portion 42; and a lower portion 46 which has the upper end thereof in open communication with a lower peripheral section of opening 44. In the assembled position, the upper end of the upper opening portion 42 is in constant open communication with the discharge end of the additive hopper 14 for the receipt of the additive material within the housing 22 and the lower end of the lower opening portion 46 is in constant open communication with the mixer assembly 16 for the discharge of additive material from housing 22 to the mixer assembly 16.The housing 22 is retained within the assembled position thereof in loader assembly 10 in any suitable manner; for example, as illustrated in Figs. 1 and 2, a co-operating bolt and flange assembly 48 carried by the housing 22 and adjacent portions of the loader assembly 10 provide a suitable releasable retention arrangement.

Metering shaft 24 is formed as a solid cylindrical rod and includes a transverse bore 50 therethrough adjacent the rear end thereof and a forwardly and radially outwardly open feed or meter cavity 52. Cavity 52 extends rearwardly from the forwardmost end of shaft 24 to a point axially intermediate the longitudinal ends of shaft 24. In the assembled position, metering shaft 24 is received through the intermediate opening portion 44 in a manner that a portion of the metering cavity 52 is received within the housing 22 and a portion of cavity 52 extends forwardly therefrom. This assembled position is maintained when rotation is imparted to shaft 24 by the output shaft assembly 54 of the drive motor 26 which is suitably releasably secured to shaft 24.As is schematically illustrated in Fig. 1 such a securing arrangement may include a cotter pin 56 or the like which extends through the transverse bore 50 and the adjacent end portion of the shaft assembly 54. Furthermore, as will be described in detail hereinafter, output shaft 54 is selectively longitudinally movable to in turn move the metering shaft 24 to adjust the length of the metering cavity 52 which is received within the housing 22.

The operational portion 58 of the metering cavity 52 is the portion thereof received within the intermediate opening 44. Additive material, such as pelletized colourant, is received within the operational portion 58 from the additive hopper 14 and discharged therefrom into the assembly 16 once during each revolution of the shaft 14. Thus, the quantity of pelletized colourant discharged to the mixer assembly 16 for mixing thereof with the material discharged into the mixer assembly 16 from the main material hopper 12, will be a function of the total volume of the operational portion 58 x the output RPM of the drive motor 26. In the embodiment illustrated, the speed of the drive motor 26 may be varied.

Hence, by selectively varying the speed of the drive motor 26 the quantity per minute of additive supplied to the mixer assembly 16 will in turn be selectively varied over a wide range. Furthermore, the invention herein includes means for adjusting the volume of the operational portion 58 by selectively moving the metering shaft 24 longitudinally to provide that a larger or shorter longitudinal extent of the metering cavity 52 is received within the intermediate opening portion 44. Thus, not only is the amount per minute out put of the additive variable by the RPM of motor 26, an even greater output range is now possible by the longitudinal movement of metering shaft 24 either independently or in conjunction with varying the RPM of the drive motor 26.

As is best illustrated in Figs. 3 to 6, a plug or end gate 60 is provided to seal the forward end of the operational portion 58 from the longitudinally adjacent exterior of the housing 22. As is shown, end gate 60 comprises a forward circular portion 62 having a radius equal to the radius of the arc from which the meterin cavity 52 is struck; and a formed rear portion 64, the periphery of which is struck from two arcs, one of which conforms exactly to the transverse periphery of the metering cavity 52 and is struck from a radius equal to the radius thereof and the other section thereof is struck from a radius equal to the radius of the shaft 24. The thickness of gate forward portion 62 is equal to the depth of forward opening portion 38 and the thickness of gate rear portion 64 is equal to the depth of rear opening portion 36.

With a construction of end gate 60 as described above, gate 60 is slidably received within cavity 52 until the rearwardly facing surface of forward portion 62 abuts the forwardly facing transition surface 66 which is formed at the juncture of opening portions 36 and 38. In this manner, the gate rear portion 64 effectively blocks or plugs the forward end of the cavity operational portion 58 and the surface 66 provides one side of the retention for gate 60 by engagement thereof with the portion of forward gate portion 62 which extends transversely outwardly from the outer periphery of shaft 24. The other side of the retention for gate 60 is provided by an end plate 68 which is suitably releasably secured, such as by bolts or the like (not shown), to the forwardly facing surface of the forward end wall 30.End plate 68 includes a coaxial bore 70 therein for the receipt of metering shaft 24 therethrough. The diameter of bore 70 is essentially equal to the diameter of the shaft 24. With such positioning, end gate 60 will be freely rotatable with the metering shaft 24 and as such it is noted that the diameter of the forward opening portion 38 is large enough such that the outermost periphery of gate portion 62 will be radially inwardly spaced from the periphery of opening portion 38 throughout the rotation of shaft 24.

A hollow cylindrical shaft shield guard 72 having an inner diameter thereof larger than the diameter of the metering shaft 24 has the rear end thereof secured to end plate 68 and extends coaxially, with respect to axis X-X, forwardly therefrom. The longitudinal extent of guard 72 is longer than the longitudinal extent of the portion of shaft 24 which extends forwardly from the housing 22. Guard 72 is included to reduce the propensity of operator injury or machinery damage which might otherwise result from having the rotat- ing shaft 24 openly exposed.

The shaft 24 is rendered longitudinally moveable in any suitable manner to provide for the heretofore mentioned volumetric adjustment of the operational portion 58 of metering cavity 52. One form of such an adjustment is illustrated in Fig. 1 wherein the drive motor 26 is carried by a support portion 74 and is rendered longitudinally moveable with respect to the support portion 74 by a rotatable adjusting screw assembly 76. With such an arrangement, if it is desired to longitudinally move the shaft 24 the adjusting screw assembly 76 is rotated in the clockwise or counterclockwise direction to longitudinally move the drive motor 26. The longitudinal movement of the drive motor 26 results in a corresponding longitudinal movement of the metering shaft 24 because of the interconnection therebetween at drive motor output shaft assembly 54.If desired, an adjusting index or scale may be provided to indicate the relative longitudinal position of the drive motor 26; for example, a suitable stationary index 78 is illustrated on the support portion 74.

The arcuate configuration of the metering cavity 52 is dictated by a variety of considerations for example: volumetric capacity; type of additive being metered; design considerations to better insure that no packing of the additives occurs within the cavity 52; and the like.

In the embodiment illustrated, the cavity 52 is structured for a pellitized colourant additive.

It is to be noted that when the metering device 20 is being used to meter pelletized additive, pellets adjacent the relatively rotating surfaces of the metering shaft 24 and housing opening 40 will become sheared rather than becoming lodged therebetween. This is a decided advantage over prior art screw or auger conveyor metering arrangements. Thus, in many instances it may be desirable that the shaft 24, housing 22 and end gate 60 be machined of high carbon steel and/or surface hardened to economically and efficiently withstand the abrasion and shear strength of the additive pellets.

An additional feature to be noted is that the metering device 20 may be efficiently and rapidly cleaned during additive changeover. In this regard, to accomplish such cleaning, the cotter pin 56 and end plate 68 are removed and the metering shaft 24 is pulled out of the housing 52. The housing 52, end gate 60 and shaft 24, may now be easily wiped, swabbed or blown clean. Furthermore, since shaft 24 is so easily removeable this enhances the rapid replacement of the metering shaft if a differing cavity configuration is desired.

Fig. 8 illustrates, partially schematically, another embodiment of a metering device 20' according to the present invention and which is similar in construction and operation to the metering device 20 described hereinbefore with the primary distinction therebetween being that the volumetric capacity of operational portion 58' of the metering cavity 24' of device 20' is adjusted by the longitudinal movement of an end gate 80 of device 20' rather than providing for such an adjustment by the longitudinal movement of the metering shaft 24 as was done hereinbefore with reference to device 20.This distinction results in other variations between the embodiments as are illustrated in the drawings and description hereinafter; however, none of such variations result in a differentiation of the basic concept of the invention of providing the metering cavity arrangement and with the capability of varying the metering device output range by volumetric and speed variations.

With metering device 20', the drive motor 26' is suitably rigidly carried by the loader assembly 10. Drive motor 26' is in suitable driving engagement with the metering shaft 24' and neither motor 26' nor shaft 24' are selectively longitudinally moveable with respect to assembly 10. The metering cavity 52' extends along the shaft 24' from the forward end thereof to adjacent the rearward end thereof. Accordingly, as illustrated, cavity 52' also extends along essentially the entire longitudinal extent of the additive receiving portion 28' of the housing 22'. The longitudinal extent of the cavity operational portion 58', and hence the volume thereof, is adjusted by the selective longitudinal movement of the end gate 80.

The end gate 80 extends longitudinally and has an irregular cross-sectional configuration which generally resembles the cross-sectional configuration of the rear portion 64 of the end gate 60 discussed hereinbefore with reference to metering device 20. The forward end of end gate 80 defines the forward longitudinal end of operational portion 58' and the rearward end of gate 80 is secured to a yoke follower member 84. Follower member 84 has a coaxial bore 86 therethrough of a diameter essentially equal to the diameter of the metering shaft 24' and a forward end portion of shaft 24' is slidably received through the bore 86.

The selective longitudinal movement of end gate 80 is provided for in any suitable manner; for example, by an adjusting screw assembly 88. Adjusting screw assembly 88 comprises a support portion 90 suitable rigidly carried by the housing 22; an adjusting screw member 92 which extends forwardly from the support portion 90 and is longitudinally moveable with respect thereto in response to rotation of a crank 94 which is carried by member 92 adjacent the forward end thereof; and a transversely extending yoke member 96 having one transverse end thereof carried by screw member 92 for movement therewith and having the other transverse end thereof co-operating with a circumferential groove 98 of yoke follower 84.Thus, with such an arrangement, rotation of crank 94 will cause a longitudinal movement of screw member 92 and a corresponding longitudinal movement of end gate 80 for the desired volumetric adjustment of operational portion 58'. The rotational movement of the crank 94 is translated to the requisite longitudinal movement by means of the yoke member 96 and the operational interconnection thereof with the yoke follower 84.

The embodiments described hereinabove are the presently preferred embodiments of the invention herein and it is to be understood that various modifications may be made thereto by those skilled in the art without departing from the scope of the invention which is defined by the appended claims. For example; a suitable guard arrangement may be provided on the metering device 20' to enclose the exposed portion of the metering shaft 24'; an indexing means may be included, if desired, on metering shaft 24' which would be co-operable with yoke follower 24 to indicate the longitudinal length of operational portion 58'; alternative means, for example a bolt and slot arrangement, are contemplated for longitudinal adjustment of the metering shafts 24 and 24'; the sequencing of operation of the metering devices 20 and 20' may be electrically or mechanically sequenced with the feed of virgin or virgin-regrind mixture to the mixture assembly; if circumstances dictate, metering devices 20 and 20' can be positioned on a loader assembly 10 to discharge into an intermediate hopper with the virgin or virginregrind mixture rather than directly into the mixer assembly 20; and the like.

Claims (11)

1. A metering device for metering particulate additive material to a moulding material prior to the charging of a plastics moulding apparatus, comprising a body member having an elongated hollow portion with vertically spaced openings extending from oppositely disposed portions of said hollow portion and longitudinally with respect to said hollow portion; an elongated selectively rotatably member closely longitudinally received within said hollow portion and having an elongated cavity therein, said cavity having at least a portion thereof rotatably moveable into and out of indexing relationship with said spaced openings for the metering of such additive during the rotation of said rotatable member; and adjusting means having at least a portion thereof received within said cavity for selectively varying the longitudinal extent of said portion of said cavity.

2. A device as claimed in claim 1, in which the longitudinal ends of said portion of said cavity are isolated from other portions of said cavity.

3. A device as claimed in claim 1 or claim 2, in which said adjusting means is operative by selectively moving said rotatable member longitudinally to adjust said longitudinal extent of said portion of said cavity.

4. A device as claimed in claim 1 or claim 2, in which said adjusting means includes a longitudinally extending gate member which co-operates with said cavity to form one of said longitudinal ends and said adjusting means is operative by selectively moving said gate member longitudinally to adjust said longitudinal extent of said portion of said cavity.

5. A device as claimed specified in any preceding claim, including selectively energizeable drive means for effecting the rotation of said rotatable member.

6. A device as claimed in claim 5, in which the rotational speed of said drive means is variable.

7. A device as claimed in any preceding claim, including externally observable indexing means for determining the longitudinal extent of said portion of said cavity.

8. A device as claimed in claim 3, in which one of said longitudinal ends remains stationary during the longitudinal movement of said rotatable member.

9. A device as claimed in claim 4, in which said gate member is rotatable with said rotatable member.

10. A device as claimed in claim 8, in which said one of said longitudinal ends is rotatable with said rotatable member.

11. A metering device for metering particulate additive material to a moulding material prior to the changing of a plastics moulding apparatus, substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 7 or Fig. 8 of the accompanying drawings.