JPH0130714B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for heating and deforming the lower part of a pilfer-proof band of a container lid fitted over a container neck.

For example, as a container lid having so-called pilfer-proof property (property to prevent tampering such as refilling of contents) for containers such as beverage bottles, Japanese Patent Application Laid-Open No. 1986-
As disclosed in Publication No. 8284, it has a top surface and a cylindrical skirt that hangs down from the periphery of the top surface, and a pilfer-proof zone is defined at the lower end of the skirt, and at least a pilfer-proof zone is defined at the lower end of the skirt. has proposed a container lid made of thermoplastic synthetic resin. Such a container lid was published in the above-mentioned Japanese Patent Application Publication No. 1983
As disclosed in Publication No. 8284, the lower part of the pilfer-proof band is heated and deformed inwardly, and the locking surface formed on the outer surface of the container neck is fitted onto the container neck. By locking, it is attached to the container neck as required.

Initially, the method of heating the lower part of the pilfer-proof band of the container lid to deform it inward was:
A method in which a heated forming tool is pressed against the lower part of the pilfer-proof band, or
As disclosed in Publication No. 8284, the lower part of the pilfer-proof strip is heated by injecting a stream of heated gas, and simultaneously or subsequently a forming tool is pressed against the lower part of the pilfer-proof strip. A method has been developed to do so. However, in such a method, when a heated or unheated forming tool is pressed against the lower part of the pilfer-proof band, the container with the container lid fitted on the container neck must be stopped at a predetermined position. Therefore, there are drawbacks such as the processing speed is limited and high-speed processing is impossible.

Therefore, Japanese Patent Application Laid-open No. 55-5389 discloses a method for solving the above-mentioned drawbacks, in which a container with a container lid fitted onto the neck of the container is transported through a predetermined path while rotating. A stream of heated gas is injected substantially horizontally from one side of the container to the bottom of the pilfer-proof zone of the container lid, without the need for pressing a forming tool against the bottom of the pilfer-proof zone. A method is disclosed in which the lower part of the pilfer-proof band is heated and deformed inward using a chisel. According to this method, there is no need to temporarily stop the container with the container lid fitted to the container neck, and therefore the processing speed is faster than the above-mentioned method using a heated or unheated forming tool. It can be increased. However, in the method disclosed in JP-A No. 55-5389, (a) the container must be transported while rotating, which inevitably limits the transport speed of the container, and the processing speed cannot be increased sufficiently. cannot be converted into (b) Requires a relatively complicated and expensive mechanism to rotate the container during transportation; (c) Heating deformation at the bottom of the pilfer-proof zone of the container lid tends to be uneven. , etc. have drawbacks.

The present invention has been made in view of the above facts, and its main purpose is to provide a device for heating and inwardly deforming the lower part of the pilfer-proof band of a container lid fitted over the neck of a container. An object of the present invention is to provide a relatively simple and inexpensive device capable of sufficiently uniformly heating and deforming the lower part of a pilfer-proof zone at a sufficient processing speed.

According to the present invention, there is provided a container lid that is fitted onto the container neck of a container having a container neck at the upper end portion with a locking surface formed on the outer surface, the container lid being fitted from the top surface and the periphery of the top surface. The pill of the container lid has a hanging cylindrical skirt, a pill-proof band is defined at the lower end of the skirt, and at least the pill-proof band is made of thermoplastic synthetic resin. A device for heating the lower part of the far-proof band to deform it inward and locking it to the locking surface of the container neck; a conveyance mechanism for conveying the container through a predetermined path without rotating; and a conveyance mechanism disposed in a heating deformation region located along the predetermined path, the container being conveyed through the heating deformation region on both sides and above the upper end of the container. a deflecting shielding hood; in the shielding hood, a flow of heated gas is directed toward a lower portion of the pilfer-proof band of the container lid fitted over the container neck of the container that is conveyed through the heated deformation region; a heated gas flow injection mechanism for injecting at least one injection port located on one side of the container conveyed through the heat deformation region at an upstream portion of the heat deformation region; at least one injection port located on the other side of the container conveyed through the heated deformation region downstream of the container, each injection port being located below the pilfer-proof zone. From the injection port located on one side of the container conveyed through the heating deformation region, the other side of the pilfer-proof band of the container lid fitted over the container neck of the container is ejected. A stream of heated gas is injected directed at the inner surface of the portion of the container, which is conveyed through the heated deformation region, from the injection port located on the other side of the container, which is fitted into the container neck of the container. and a heated gas flow injection mechanism for injecting a heated gas flow directed toward the inner surface of a portion of the container lid located on one side of the pilfer-proof zone; is provided.

A more detailed description will be given below with reference to the accompanying drawings.

First of all, an example of an object to be processed by an apparatus constructed according to the present invention, namely a container and a container lid fitted to the container neck of the container, will be described.
This will be explained with reference to FIG.

The container 2, which can be formed from glass or a suitable synthetic resin, has a container neck 4 at its upper end (FIG. 1 shows only the upper end of the container 2, that is, the container neck 4). . Illustrated container neck 4
has a cylindrical shape with an open upper end, and a male thread 6 is formed on its outer surface. Further, an annular protrusion 8 is formed on the outer surface of the container neck 4 and extends continuously in the circumferential direction and is located below the male thread 6. Thus, a locking surface is defined to which the lower part of the pilfer-proof band of the container lid is locked.

On the other hand, the illustrated container lid, whose entirety is designated by the numeral 10 and which is fitted onto the container neck 4, is made entirely of a suitable thermoplastic synthetic resin such as polyethylene or polypropylene. and a cylindrical skirt 14 depending from the periphery of surface 12. It is desirable that an annular seal part 16 of an appropriate shape to be engaged with the edge of the container neck 4 is formed on the inside of the top surface 12. If desired, instead of forming a pair of annular seals 16 on the inside of the top 12, a separate packing member formed in an appropriate shape can be provided inside the top 12. On the other hand, the skirt 14 is formed with a weakened line 18 extending in the circumferential direction, and the skirt 14 has a relatively thick main portion 20 located above the weakened line 18 and a weakened line 18.
It is divided into a relatively thin pilfer-proof zone 22 located below. Weakening line 1
8 itself can be defined by a so-called score or the like in which the material thickness is reduced, but in the illustrated case, a plurality of slits 24 extending in the circumferential direction at intervals in the circumferential direction and the slits 24 The pilfer-proof zone 22 is connected to the main portion 20 by the plurality of bridges 26 located therebetween. The inner surface of the main portion 20 has a female thread 2 which is screwed into a male thread 6 formed on the outer surface of the container neck 4.
8 is formed. Further, knurling or unevenness 30 is formed on the outer surface of the main portion 20,
It is advantageous that the container lid 10 can be securely and easily gripped and rotated with fingers.

Such a container lid 10 is attached to the container neck 4 in the following manner.

First, the container lid 10 is fitted onto the container neck 4, and then, in the illustrated case, the container lid 10 is placed in the first position.
Rotate clockwise when viewed from above in the figure. In this way, the female thread 28 formed on the container lid 10 is screwed into the male thread 6 formed on the container neck 4, and the container lid 10 is moved downward in the axial direction as it rotates, and the container lid 10 is rotated and moved downward in the axial direction. The container lid 10 is positioned relative to the mouth and neck 4 as shown in FIG. In the state shown in Figure 1,
An annular seal portion 16 formed inside the top surface 12 of the container lid 10 is engaged with the edge of the container neck 4 with a required pressure, thus sealing the container neck 4. In addition, in the specific example shown, as can be understood from FIG. It is brought into contact with or close to the end 8b.

Next, the container 2 with the container lid 10 fitted onto the container neck 4 in the state shown in FIG.
Processed by the apparatus illustrated in the figure. Referring now to FIG. 2, which illustrates a preferred embodiment of an apparatus constructed in accordance with the present invention, generally designated at 32
The illustrated device has a container lid 10 on the container neck 4.
A transport mechanism 3 for transporting the container 2 fitted with
It is equipped with 4. The illustrated transport mechanism 34 includes an endless transport belt 38 that is driven in the direction indicated by arrow 36 by a suitable drive source (not shown) such as an electric motor. The containers 2 are transported to an endless conveyor belt 38 by a suitable feeding mechanism (not shown).
Accompanying the movement of the endless conveyor belt 38, which is placed upright on the upper run of the belt and is thus driven in the direction indicated by arrow 36, a predetermined path defined by the upper run of the endless conveyor belt 38 is created. transported through.

In the illustrated device 32, an endless conveyor belt 3
8, along a predetermined path of the container 2 transported by the transport mechanism 34 having the liquid application area 4.
4 is located, and a heating deformation region 46 is located downstream of this liquid application region 44. As will be described in detail later, in the liquid application area 44, a liquid application process is performed as a pretreatment, and the heating deformation area 46
In this case, the lower part of the pilfer-proof band 22 of the container lid 10 is heated and deformed inward, and is locked to the locking surface formed on the outer surface of the container neck 4, that is, the lower surface 8a of the annular protrusion 8. (See also Figure 1).

The liquid application area 44 includes a pair of shielding walls 4 located on both sides of the container 2 transported by the transport mechanism 34.
8 are arranged. Each of the pair of shielding walls 48, supported in position by suitable support means (not shown), has at least one, and in the case shown three, projecting inwardly therethrough. A liquid jet nozzle 50 is provided. Each of the liquid injection nozzles 50 is connected to a suitable liquid supply source (not shown) and sprays a liquid, which may be water, for example, from an injection port located between the pair of shielding walls 48. The liquid is ejected from the ejection ports of at least one pair (in the case of illustration, three pairs) of liquid ejection nozzles 50 located opposite to each other on both sides of the container 2 transported by the transport mechanism 34, as shown in FIG. , is preferably directed towards the lower part of the skirt 14 of the container lid 10 fitted over the container neck 4 of the container 2, in particular towards the weakened line 18. The liquid that can be used as water may normally be one at room temperature, but if the container 2 is made of glass and the contents of the container are heated and filled high-temperature liquids, the temperature of the glass container 2 due to thermal distortion may occur. To avoid breakage, e.g.
It is desirable to inject heated liquid such that the temperature difference does not exceed 40 degrees.

Most of the liquid injected from the injection port of the liquid injection nozzle 50 flows down along the outer surface of the skirt 14 of the container lid 10 and the outer surface of the container 2. If the skirt 14 of the container lid 10 or the outer surface of the container 2 has contents or dust scattered during filling, for example, the flowing liquid will wash them away.
On the other hand, a part of the injected liquid flows through the weakened line 18
The pilfer-proof strip 22 enters between the outer surface of the container neck 4 and the inner surface of the skirt 14 of the container lid 10 through the slit 24 defining the The residual liquid 52 remains in the space between the inner surface of the upper part and the outer surface 8c of the annular protrusion 8 formed on the outer surface of the container mouth neck 4 (the effects obtained by producing such residual liquid 52 will be explained in detail later). ). In the liquid application area 44, if necessary, a collection path (not shown) for collecting the liquid jetted from the jetting port of the liquid jetting nozzle 50 and flowing down may be provided, for example, below the endless conveyor belt 38. will be placed.

Next, the heat deformation region 46 will be explained with reference to FIG. 5 together with FIG.
, a shielding hood 54 is provided above the upper running portion of the endless conveyor belt 38. The illustrated shielding hood 54 is supported in position by suitable support means (not shown).
has an upper wall 56 and both side walls 58a and 58b depending from both side edges of the upper wall 56. Top wall 56 and side walls 58, as will be readily understood by referring to FIG. 6 in conjunction with FIGS. 2 and 5.
extends along the path of the container 2 conveyed through the heating deformation region 46 by the endless conveyor belt 38,
At least the upper end portion (namely, the container neck portion 4 into which the container lid 10 is fitted) of the container 2 transported through the heating deformation region 46 is bent on both sides and above. In the illustrated embodiment, the side walls 58a and 58b of the shield hood 54 depend downwardly to a level near the bottom end of the container 2, such that the shield hood 54 surrounds the top of the container 2 and substantially the entirety of the container on both sides. It's bending.

The heated deformation region 46 is further provided with a heated gas flow injection mechanism 60 . In the illustrated example, the heated gas injection mechanism 60 includes a pair of heated gas injection nozzles 62a and 62b. As clearly shown in FIG. 5, one 62 of a pair of heated gas flow injection nozzles 62a and 62b
a is one 58 of both side walls 58a and 58b of the shielding hood 54 in the upstream part of the heat deformation region 46.
a and protrudes into the shielding hood 54.
The projecting end of the heated gas jet nozzle 62a is provided with a container 2 that is conveyed through the heating deformation region 46.
One or more elongated injection ports 64a, preferably three elongated injection ports 64a, which are preferably arranged in a straight line along the path of the container 2, are formed along the path of the container 2. . The other 62b of the pair of heated gas flow injection nozzles 62a and 62b is connected to the shielding hood 54 at a downstream portion of the heating deformation region 46.
It protrudes into the shielding hood 54 through the other of the side walls 58a and 58b. The protruding end of the heated gas flow injection nozzle 62b preferably has an elongated shape extending along the path of the container 2 conveyed through the heating deformation region 46, as in the case of the heated gas flow injection nozzle 62a. One or more, in the illustrated case, three elongated injection ports 64b arranged in a straight line along the path of the container 2 are formed. Heated gas flow injection nozzles 62a and 6
As shown in FIG. 6, the injection ports 64a and 64b of the container 2b are located below the pilfer-proof band 22 of the container lid 10 fitted onto the container neck 4 of the container 2 conveyed through the heating deformation region 46. Being located is important. The pair of heated gas jet nozzles 62a and 62b are heated at temperatures of, for example, 200°C to 300°C.
The container 2 is connected to a source of heated gas (not shown), which may be heated air heated to a certain degree, and is fitted onto the container neck 4 of the container 2 being conveyed through the heating deformation region 46, as will be described in detail later. Container lid 10
A heated gas stream is injected from injection ports 64a and 64b toward the pilfer-proof zone 22 (see also FIG. 1).

In the illustrated example, the injection ports 6 of the pair of heated gas flow injection nozzles 62a and 62b are further provided.
4a and 64b, a shielding hood 5
A pair of guide plates 66a and 66b are provided that protrude from the inner surfaces of both side walls 58a and 58b of 4. More specifically, in the upstream portion of the heat deformation region 46, a guide plate 66a protrudes substantially horizontally from the inner surface of the other side wall 58b of the side walls 58a and 58b of the shielding hood 54, and in the downstream portion of the heat deformation region 46, Both side walls 58a and 5 of the shielding hood 54
A guide plate 66b projects substantially horizontally from one side 58a of the guide plate 8b. Each of the guide plates 66a and 66b projects substantially horizontally toward the pilfer-proof band 22 fitted over the container neck 4 of the container 2 being conveyed through the heating deformation region 46, as shown in FIG. It is preferable that

The action in the heating deformation region 46 as described above is as follows. In the upstream part of the heating deformation area 46, as shown in FIG.
A stream of heated gas is injected from the The heated gas flow is injected upward from the injection port 64a,
The pilfer-proof band 22 of the container lid 10 fitted onto the container neck 4 of the container 2 is oriented toward the inner surface of the portion located on the other side (that is, the portion located on the left side in FIG. 7). is important. The above-mentioned heated gas flow injected from the injection port 64a heats the portion of the pilfer-proof zone 22 of the container lid 10 located on the other side, especially the lower inner surface of the portion, and On the inner surface, the thermoplastic synthetic resin material is softened and contracted by residual stress caused by molecular orientation during molding. Further, the heated gas flow as described above injected from the injection port 64a passes through the front and rear of the container lid 10 and the upper wall 56 and side wall 58b of the shielding hood 54, as shown in FIG.
container lid 10 by colliding with the inner surface of the container lid 10 and then flowing along the guide plate 66a or directly.
The liquid flows toward the outer surface of the portion of the pilfer-proof zone 22 located on the other side, and heats the outer surface of this portion to some extent. Heated gas flow injection nozzle 6
Due to the action of the above-mentioned heated gas flow injected from the injection port 64a of 2a, in the upstream portion of the heating deformation region 46, the pilfer-proof zone 22 of the container lid 10 is located on the other side. The lower portion of the approximately half portion is heated and deformed inward, and is locked to the locking surface (ie, the lower surface 8a of the annular protrusion 8) formed on the container neck 4 as required.

On the other hand, in the downstream part of the heating deformation region 46,
As shown in FIG. 8, the heated gas stream is injected from the injection port 64b of the heated gas stream injection nozzle 62b located on the other side of the container 2 being conveyed through the heating deformation region 46. This heated gas flow is transmitted through the injection port 6
4b and is sprayed upward from the container neck 4 of the container 2, the part located on one side of the pilfer-proof band 22 of the container lid 10 (that is, the part located on the right side in FIG. 8). It is important that it is directed towards the inner surface of the body part). By the heated gas flow as described above injected from the injection port 64b,
The portion located on one side of the pilfer-proof zone 22 of the container lid 10, especially the inner surface of the lower portion thereof, is heated, and the thermoplastic synthetic resin material on the inner surface of this portion is softened and the molecular orientation during molding, etc. It is caused to contract by the action of residual stress caused by. Further, the heated gas flow as described above injected from the injection port 64b passes through the front and rear of the container lid 10, and the inner surfaces of the upper wall 56 and side wall 58a of the shielding hood 54, as shown in FIG. , and then flows along the guide plate 66b or directly toward the outer surface of the portion of the pilfer-proof zone 22 of the container lid 10 located on the one side, Heats up the outer surface somewhat. Due to the action of the above-described heated gas flow injected from the injection port 64b of the heated gas flow injection nozzle 62b, the pilfer-proof zone 22 of the container lid 10 is
The lower part of the remaining half located on the one side is heated and deformed inward, and the locking surface formed on the container neck 4 (i.e., the lower surface 8 of the annular protrusion 8) is heated and deformed inward.
a) is locked as required.

As described above, after being subjected to the action of the heated gas flow as described above in the upstream and downstream parts of the heating deformation region 46, the container neck 4 of the container 2 as shown in FIG. The entire lower part of the pilfer-proof band 22 of the fitted container lid 10 is deformed inward, and the locking surface (i.e., the lower surface 8a of the annular protrusion 8) formed on the container neck 4 is formed as required. The container lid 10 is thus secured to the container neck 4 of the container 2 as required.

In view of the results of various experiments carried out by the present inventors, it is possible to efficiently utilize the heat of the heated gas flow in the heating deformation region 46 and to heat the entire lower part of the pilfer-proof zone 22 sufficiently uniformly. In order to deform, the upper wall 56 of the shielding hood 54 is attached to the container 2.
It is desirable that the container lid 10 is placed as close as possible to the top surface of the container lid 10 fitted over the container neck 4. Generally, it is desirable that the distance between the inner surfaces of both side walls 58a and 58b of the shielding hood 54 be about 2 to 4 times the outer diameter of the container lid 10. Further, the distance between the protruding edges of each of the guide plates 66a and 66b protruding from the inner surfaces of the side walls 58a and 58b of the shielding hood 54 and the outer surface of the pilfer-proof band 22 of the container lid 10 is generally as follows. It is desirable that it be about 20 to 35 mm.

On the other hand, as understood from FIGS. 7 and 8,
When the container 2 with the container lid 10 fitted on the container neck 4 is conveyed through the heating deformation region 46, the injection ports 6 of the heated gas flow injection nozzles 62a and 62b
The heated gas flow injected from 4a and 64b hits not only the bottom but also the top of the pilfer-proof zone 22 of the container lid 10. Therefore, in the normal case,
Heat is also applied to the top of the pilfer-proof zone 22, which may cause undesirable deformation of the top of the pilfer-proof zone 22. However, in the specific example shown, the liquid application area 44 is arranged upstream of the heating deformation area 46, and the liquid application area 44 is provided with the liquid application as described with reference to FIGS. 3 and 4. Because the process is carried out, undesired deformations in the upper part of the pilfer-proof zone 22 are largely prevented. To further discuss this point, as described above, the liquid application process in the liquid application area 44 causes the inner surface of the upper part of the pilfer-proof zone 22 of the container lid 10 and the annular shape of the container neck 4 to be formed as shown in FIG. A residual liquid 52 is generated in a space between the protrusion 8 and the outer surface 8c in contact with the inner surface of the upper part of the pilfer-proof band 22. Therefore, when heat is applied to the top of the pilfer-proof zone 22 by the heated gas flow in the heated deformation region 46, the residual liquid 5
2 is evaporated, and the upper part of the pilfer-proof zone 22 is effectively cooled by the heat of vaporization during evaporation. Therefore, the upper part of the pilfer-proof zone 22 is effectively prevented from being softened, melted, and deformed, and even after the heating and deforming step, the pilfer-proof zone 22 remains as shown in FIG.
The upper part of the is substantially undeformed and assumes the desired appearance.

Although preferred specific examples of the apparatus configured according to the present invention have been described above in detail with reference to the accompanying drawings, the present invention is not limited to such specific examples, and there may be no deviation from the scope of the present invention. Needless to say, various modifications and modifications are possible.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway side view showing an example of a container and a container lid fitted over the container neck of the container, which are processed by an apparatus constructed according to the present invention. FIG. 2 is a perspective view of a preferred embodiment of an apparatus constructed in accordance with the present invention. FIG. 3 is a partially cutaway sectional view for explaining the liquid application process performed in the liquid application area of the apparatus shown in FIG. 2; FIG. 4 is a sectional view showing residual liquid generated in the liquid application step shown in FIG. 3. FIG. 5 is a partially cutaway perspective view showing a shielding hood and a heated gas flow injection mechanism disposed in the heating deformation region of the apparatus shown in FIG. 2; FIG. 6 is a sectional view showing a heating deformation region in the apparatus shown in FIG. 2. FIG. 7 is a partial cross-sectional view for explaining the action at the upstream portion of the heating deformation region in the apparatus shown in FIG. 2. FIG. 8 is a partial cross-sectional view for explaining the action downstream of the heating deformation region in the apparatus shown in FIG. 2. FIG. 9 is a partial cross-section showing, with a portion cut away, the container and the container lid fitted as required on the container neck of the container after undergoing the heating deformation process in the apparatus illustrated in FIG. 2; figure. 2... Container, 4... Container neck, 8... Annular protrusion, 8a... Lower surface (locking surface) of annular protrusion, 10...
...Container lid, 12...Top surface, 14...Skirt, 2
2...Pilfer proof band, 32... Entire device, 34... Conveyance mechanism, 44... Liquid application area, 4
6... Heat deformation area, 54... Shielding hood, 60
...Heated gas flow injection mechanism, 62a and 62b...
Heated gas flow injection nozzles, 64a and 64b... injection ports, 66a and 66b... guide plates.

Claims (1)

[Scope of Claims] 1. A container lid that is fitted over the container neck of a container having a container neck at the upper end with a locking surface formed on the outer surface, which comprises a top surface and a periphery of the top surface. a cylindrical skirt that hangs down from the container lid, a pilfer-proof zone is defined at the lower end of the skirt, and at least the pilfer-proof zone is made of a thermoplastic synthetic resin. A device for heating the lower part of the pilfer-proof band to deform it inward and locking it to the locking surface of the container neck; , a conveyance mechanism for conveying the container through a predetermined path without rotating; and a conveyance mechanism disposed in a heating deformation area located along the predetermined path, and at least both sides of and above the upper end of the container to be conveyed through the heating deformation area. a shielding hood enclosing; in the shielding hood, heating gas is directed toward a lower portion of the pilfer-proof band of the container lid fitted over the container neck of the container that is conveyed through the heating deformation region; a heated gas flow injection mechanism for injecting a gas flow, at least one jet orifice located upstream of the heating deformation region and on one side of the container conveyed through the heating deformation region; at least one jet orifice located on the other side of the container conveyed through the heating deformation region downstream of the zone, each of the jets being located below the pilfer-proof zone. From the injection port located on one side of the container being conveyed through the heating and deforming region, the other of the pilfer-proof bands of the container lid fitted over the container mouth neck of the container is emitted. A stream of heated gas directed to the inner surface of the portion located on the side is injected from the injection port located on the other side of the container, which is conveyed through the heating deformation region, and is conveyed through the heating deformation region. and a heated gas flow injection mechanism for injecting a heated gas flow directed toward the inner surface of a portion of the pilfer-proof zone of the container lid, which is located on one side of the pilfer-proof zone. Device. 2. Each of the injection ports of the heated gas flow injection mechanism is
2. The device of claim 1, wherein the device is elongated and extends along the predetermined path. 3. The shielding hood has an upper wall extending along the predetermined path above the container being conveyed through the heating deformation region, and both side walls depending from both side edges of the upper wall. The device according to item 1 or 2. 4. The shielding hood is further directed toward the pilfer-proof band of the container lid fitted over the container neck of the container being conveyed through the heating deformation region.
4. The apparatus of claim 3, further comprising a pair of guide plates projecting substantially horizontally from the inner surface of each of the side walls opposite each of the injection ports.