Molding machine with mold block carriage

Details Molding machine with mold block carriage Molding machine with mold block carriage

1999-03-01

2001-02-27

Pyon, Harold (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

Sets of press couples comprising registering female mold...

C425S326100, C425S336000, C425S370000, C425S392000, C425S396000, C425S453000

Reexamination Certificate

active

06193496

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field
The present invention is directed toward machines for molding objects, and more particularly toward carriages for use in positioning the mold blocks in such machines.
2. Background Art
A well known method for manufacturing corrugated pipes is to extrude a tube of thermoplastic from a head and then conform that tube to the interior of a corrugated mold tunnel formed by mold blocks. The mold blocks typically come in pairs and mate together to form a portion of the mold tunnel, and the thermoplastic is either blown into its shape (by pressure created within the mold tunnel) or by vacuum (where vacuum draws the air from around the mold tunnel).
Structures which have been used in the vacuum method of manufacture are illustrated in U.S. Pat. Nos. 4,319,872, 4,439,130, and 4,718,844. These patents all address the problem of drawing a uniform, strong vacuum around the entirety of the mold blocks which are continually moving during the molding process.
Moving and properly aligning multiple mold blocks is important to ensure that the formed product is continuously uniform along its length without distortions which could occur if the mold blocks are not properly aligned relative to each other. In clamshell type machines, for example (with the mold blocks supported on a single carriage on one side), any forces incurred on the other side of the mold blocks naturally involves a larger moment arm about the carriages, with the result being that such structures can be more susceptible to “sawtooth” type arrangements through the mold tunnel, with successive mold blocks being tilted slightly rather than perfectly aligned with the axis of the mold tunnel.
In order to properly align the mold blocks, it has been found to be advantageous to carry the mold blocks on carriers which themselves have wheels which ride in a track about the path desired for the mold blocks. In order to secure the carriages in the track, the wheels must generally be trapped by opposite sides of the track. In such cases, clearance must be provided (i.e., the opposite track sides must be spaced apart a distance which is greater than the wheel diameters) to allow the wheels to roll on one side without dragging on the other. Such clearance can, however, result in some looseness of the carriage, thereby allowing some degree of sawtoothing. One structure which has been used to address this is shown in U.S. Pat. No. 5,489,201, in which an extra roller is provided along the sides of the carriages, such extra wheel being offset from the other carriage wheels so that it will roll along the top of the machine track while the other carriage wheels roll along the bottom of the machine track.
Rollers have also been provided on carriages and similarly guided in tracks to secure the carriages against lateral shifting during motion. U.S. Pat. No. 4,439,130 shows such a structure. The clearance which must be provided with those rollers (again to prevent the wheel from dragging on one side of the track while rolling on the other side) does, however, potentially allow some degree of undesirable lateral shifting of the carriage and carried mold blocks.
The present invention is directed toward overcoming one or more of the problems set forth above.
SUMMARY OF THE INVENTION
In one aspect of the present invention, a carriage for carrying a mold block along an axially extending molding section of a molding machine is provided. The carriage is adapted for use with a molding machine including axially extending tracks on opposite sides, an axially extending central guide track between the side tracks, and four sets of rollers each defining an axial extending rolling plane, two of the sets of rollers being associated with one of the side tracks with parallel facing rolling planes and the other two of the sets of rollers being associated with the other of the side tracks with parallel facing rolling planes. The carriage includes a carriage body having a connector adapted to secure at least one mold block to the carriage body and oppositely facing flat surfaces on opposite sides of the carriage body. The oppositely facing flat surfaces on one side are adapted to engage the two sets of rollers when located in the molding section of the molding machine and the oppositely facing flat surfaces on the other side are adapted to engage the other two of the sets of rollers when located in the molding section of the molding machine. Wheel sets are provided on opposite sides of the carriage body and are adapted to roll in the machine side tracks when located in the molding section of the molding machine. Centering rollers on the carriage body are adapted to roll on opposite sides of the central guide track when located in the molding section of the molding machine.
In a preferred form of this aspect of the present invention, the connector comprises a pivot adapted to secure two mold blocks for selective pivoting about an axis generally disposed centrally between the carriage body opposite sides.
In another aspect of the present invention, a molding machine is provided, including a plurality of carriages for carrying mold blocks in an axial direction and a track for the carriages including a molding section. The carriages each include wheels on opposite sides of the carriage, a first set of oppositely facing and axially extending flat surfaces adjacent the wheels on one side of the carriage, and a second set of oppositely facing and axially extending flat surfaces adjacent the wheels on the other side of the carriage. The track includes spaced apart channels receiving the carriage wheels for guiding the carriages along the track. Along the molding section the track further includes first and second sets of track rollers defining a first pair of parallel, axially extending facing rolling planes whereby the first and second roller sets engage the first set of flat surfaces of carriages in the molding section, and third and fourth sets of track rollers defining a second pair of parallel, axially extending facing rolling planes whereby the third and fourth roller sets engage the first set of flat surfaces of carriages in the molding section.
In a preferred form of this aspect of the present invention, centering rollers are also provided on the carriages having facing rolling surfaces spaced apart a distance X, and a central guide track is disposed between the channels along the molding section and engaged on opposite sides by the centering rollers of carriages in the molding section, the engaged opposite sides of the central guide track being spaced apart the distance X.
In another preferred form of this aspect of the present invention, each of the carriages includes a mold block pivot mount adapted to mount mold blocks for pivoting about a block pivoting axis extending in the axial direction.
In still another preferred form of this aspect of the present invention, the flat surfaces of each flat surface set are spaced apart a distance Y, the parallel facing rolling planes of the first and second sets of rollers are spaced apart the distance Y, and the parallel facing rolling planes of the third and fourth sets of rollers are spaced apart the distance Y.
In yet another preferred form of this aspect of the present invention, the sets of track rollers each comprise a plurality of rollers having the same radii and mounted for rotation about pivot axes substantially parallel to one another and disposed in a plane spaced from and substantially parallel to the engaged flat surfaces. In a further preferred form, the spacing between the first set of flat surfaces plus the radius of the first track rollers plus the radius of the second track rollers equals distance Z, and the planes defined by the first and second track roller pivot axes are spaced apart the distance Z.
In still another aspect of the present invention, a molding machine is provided including a plurality of carriages for carrying mold blocks in an axial direction and a track for the carriages including a molding section, the track including spaced apart channels rec

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