Slide Retainer And Positioner

Abstract

A slide retainer and positioner for molds having at least one cam-actuated slide for pulling a core element laterally of the mold cavity as the mating mold parts are opened, said slide retainer and positioner being embodied wholly within the mold at all times and adapted to yieldingly clamp the slide in cam-aligned position only when the mold is opened without restraining the opening and closing movement of the slide.

Description

BACKGROUND OF THE INVENTION

In conventional molds for injection molding, for example, in addition to the mating parts which are designed to abut each other at a parting line, and to move directly away from each other when the mold is opened, there are usually one or more core parts which move laterally into and out of the mold cavity as the mold is closed and opened. These core parts are connected to slides in the mold and the slides are actuated by closing and opening movement of the mating parts through inclined cams or pins on one part slidably engaging cam surfaces or inclined bores on another part.

Normally the opening movement of the mating mold parts continues beyond the point where the cam pins become disengaged from the interfitting inclined bores, and it is necessary that the pins and bores be maintained in alignment so that during the closing movement the pins will re-enter the bores and actuate the slides to move the core parts into position within the mold cavity. When the mold is opened the slides tend to move into misaligned positions for several reasons: for example, by gravity if they are in an overhead position, accidental bumping of the slides by the operator, or moving the slides due to pulling the product from the mold cavity in production runs.

To avoid such misalignment conventional molds have usually been provided with exterior pre-loaded compression spring retainers attached to the slides and projecting outwardly of the mold to hold the slides in laterally outward position with the cam pins and bores aligned after the pins become disengaged during mold opening movement.

There are a number of disadvantages resulting from the use of these compression spring retainers. First, the spring retainers have to be positioned to extend outwardly between the tie rods of the molding machine, and whenever the mold is inserted or removed from the machine it is necessary to remove all of the projecting parts of the spring retainer assemblies in order to get the mold past the tie rods. Second, pre-loading the retainer springs requires an additional assembly operation, and when the mold is closed and the springs are fully compressed, there is always danger of breakage of the spring assemblies with consequent injury to workmen and loss of production time. In some cases safety housings for the springs have been provided but this adds expense and does not prevent loss of production time if the spring breaks. Third, the pressure of the spring retainers is applied to the slidably engaging surfaces of the pins and bores during the entire movement of the pins therein, with consequent galding of the engaging surfaces. Fourth, in preparing the mold for shipment an extra large crate is required to enclose the projecting spring retainers, and an additional clamping plate is required to hold the mold parts together against the opening action of the retainer springs.

SUMMARY OF THE INVENTION

It is a general object of the present invention to provide an improved and inexpensive slide retainer and positioner for molds which will overcome the disadvantages of prior constructions.

Another and more specific object is to provide an improved slide retainer and positioner which is embodied wholly within the mold so as not to interfere with the machine tie rods during operation or during installation or removal of the mold from the machine.

A further object is to provide an improved slide retainer and positioner which does not require a separate housing for protection in case of breakage as it is always fully enclosed within the mold.

Another object is to provide an improved slide retainer and positioner in which spring pressure is applied to the slidably engaging surfaces of the cam actuating means only at the end of the slide-opening movement so as to minimize frictional wear on said surfaces.

A still further object is to provide an improved slide retainer and positioner which does not increase the crating size of the mold for shipment, and which does not require additional clamping means to hold the mold parts together during shipment.

These and other objects are accomplished by the improvements and combinations of elements comprising the present invention, a preferred embodiment of which is shown by way of example in the accompanying drawings and hereinafter described in detail. Various modifications and changes in details of construction are comprehended within the scope of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of an injection molding machine having mating mold parts embodying the improved slide retainers and positioners.

FIG. 2 is an enlarged partial sectional view through a similar mold of an injection molding machine equipped with the prior conventional compression spring retainers for holding the slides in laterally outward aligned positions when the mold is fully opened.

FIG. 3 is an enlarged vertical sectional view of the mold of FIG. 1 in closed position, taken substantially on line 3--3 of FIG. 5.

FIG. 4 is a similar view showing the mold in fully open position.

FIG. 5 is a plan sectional view on the mold parting line on line 5--5 of FIG. 3.

FIG. 6 is an enlarged partial plan view of one of the improved slide retainers.

FIG. 7 is an enlarged partial sectional view on line 7--7 of FIG. 5.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to FIG. 1, a simple injection molding machine is shown therein somewhat schematically, comprising the material feed hopper 10, the housing 11 for the ram and heater, the nozzle 12, the mold parts indicated generally at 13a and 13b held together between stationary pressure plate 14 and movable pressure plate 15. Plate 14 is supported on a base 16 and is connected by tie rods 17 to a plate 18 mounted on the base and supporting one end of the fluid cylinder 19 for actuating the movable pressure plate 15. Cylinder 19 has a piston rod 20 connected to the movable plate 15, on which mold part 13b is mounted, for reciprocating it on the tie rods to open and close the mold.

Referring now to FIGS. 3 - 5, the mating mold parts 13a and 13b abut each other at the parting line P in closed position, forming between them four like mold cavities 22 for molding parts therein. The feed material from the hopper 10 is heated and then injected by the ram through nozzle 12 and sprue 23 to the runner 24 and thence through gate openings 25 into the cavities 22. Core plates 26 extend laterally into each pair of cavities 22 at the parting line. Extending axially of the mold part 13b are four bores, one from each cavity 22, in which knock-out rods 27 may be mounted for aiding in removal of the molded parts when the mold is opened. The knock-out rods are operated by a knock-out plate 28, in a usual manner.

The mold parts thus far described may be substantially the same as those shown in the prior conventional construction of FIG. 2, as indicated by the same reference numerals, and per se form no part of the present invention.

In order to move the core plates 26 laterally out of the mold cavities as the mold is opened, the mold part 13a is provided with cam elements or horn pins 30, one for each core plate 26, which are inclined to the parting line and in planes parallel to the direction of movement of mold part 13b. These horn pins are rigidly secured in mold part 13a and slidably engage inclined cam surfaces or bores in slides connected to the core plates 26 to move the core plates laterally out of the mold cavities as the mold is opened by moving part 13b away from part 13a on the tie rods 17. Recesses 31 and 32 are provided in the plates of mold part 13b to receive the horn pins in mold closed position.

The inclined bores 34 for the horn pins are formed in slides 35 mounted for lateral sliding movement in guide rails 36 on opposite sides of the slide having flanges overlying side flanges on the slides. The slides and guide rails are mounted in recesses 37 in mold part 13b at the parting line P, and the recesses 37 extend laterally outward a sufficient distance to accommodate the improved slide retainers for holding the slides in aligned positions with the horn pins after the pins have moved out of the bores 34 when the mold is fully opened, as shown in FIG. 4.

The outer edges of the core plates 26 are recessed into the inner ends of the slides 35 and are secured thereto by screws 38, and the surfaces of the slides merge with the surfaces of the core plates at the parting line P. The opposite surfaces of the slides slide on wear plates 39 secured in the bottoms of recesses 37. The outer ends of the slides have inclined surfaces parallel to the horn pins which in mold-closed position engage similarly inclined surfaces on pressure pads 40 secured to the mold part 13a by screws 41 to lock the slides in place.

The improved slide retainers indicated as a whole at 43 are mounted in sub recesses 44 within the recesses 37 below the level of the slides and laterally outward of the slides in the closed position of the mold. The retainers each comprise a pair of opposed jaw elements 45a and 45b having interengaging clevises 46a and 46b intermediate their ends pivoted on a stud 47 screwed into the base of the sub recess 44. A pre-loaded compression spring 48 is interposed between the outer ends of the jaw elements, and their inner ends are provided with opposed cam surfaces 49 connected to undercut arcuate surfaces 50 for yieldably receiving and clamping a dowel pin 51 secured in and depending from the outer end of the slide 35.

In the operation of the improved slide retainers 43, as the mold is opened by moving mold part 13b away from mold part 13a, the sliding engagement of the horn pins 30 with the bores 34 moves the slides and the connected core plates 26 laterally outward of the mold cavities. At the point where the pins 30 become disengaged from the bores 34, the dowel pins 51 enter between the cam surfaces 49 of the jaws forcing them slightly apart against the pressure of spring 48 until the pins 51 are yieldably engaged by the arcuate surfaces 50. Thus the slides are retained in position with the bores 34 aligned with the adjacent ends of the pins 30, so that when the mold is again closed the pins will enter the bores. It will be apparent that when the mold closing movement is initiated by fluid pressure, the pins 51 will force the jaws to open and release the pins, after which there is no restraining pressure on the sliding movement of the horn pins 30 in the bores 34. Likewise, the retainers exert no restraining movement on this sliding movement during the mold opening movement. Thus, there is no galding of the slidingly engaging surfaces caused by the slide retainers 43.

The novel slide retainer and positioner is embodied wholly within the mold so as not to interfere with machine tie rods during operation of the machine or while changing molds, and there is no danger from breakage as the springs and retainer assemblies are always fully enclosed, and no requirement for separate spring housings. The spring retainer operates only when the horn pins are disengaged from their cooperating bores so that no restraining force is exerted on the slidingly engaging surfaces of the pins and bores during the mold opening and closing movements and no opening force tending to open the mold when assembled for shipment. Moreover, since there are no projecting spring retainer assemblies the shipping size of the mold is minimized.

Referring to the prior art construction of FIG. 2, the slides 135 are connected to pull rods 155 which project outwardly of the mold, and each slide is urged laterally outward by a pre-loaded compression spring 156 interposed between the washer 157 at the outer end of the rod 155 and a stop plate 158 on the side of the mold part 13b against which the slide abuts when fully retracted. A safety spring housing is indicated at 160 which projects beyond the end of rod 155 sufficiently to allow for the retraction movement.

It will be apparent that all of the disadvantages listed herein under "Background of the Invention" are present in this prior art construction and that all of said disadvantages are overcome by the present improved slide retainer and positioner.

Claims

1. In a mold having at least two mating parts abutting at a parting line and forming a mold cavity and at least one cam-actuated slide for moving a core part laterally outward and inward of said cavity during opening and closing of the mold, the improvement comprising slide retainer and positioner means wholly enclosed within the mold and having spring-biased jaws for yieldingly gripping an element on the slide to hold it in aligned position only at the end of the cam-actuated laterally outward movement thereof and releasing said element at the beginning of the cam-actuated

2. In a mold as described in claim 1, in which the cam-actuated movement of the slide is effected by an inclined cam pin on one mold part slidably engaging an inclined bore on the slide and the jaws grip the slide element when the pin leaves the bore during opening movement of the mold parts.

3. In a mold as described in claim 2, in which the spring-biased jaws comprise a pair of jaws pivotally connected intermediate their ends, said jaws having opposed jaw surfaces at one end and compression spring means

4. In a mold as described in claim 3, in which the gripped element on the slide is a dowel pin and the jaws have cooperating cam surfaces for

5. In a mold as described in claim 2, in which the gripped element on the slide is a dowel pin and the jaws have cooperating cam surfaces for

6. In a mold as described in claim 1, in which the spring-biased jaws comprise a pair of jaws pivotally connected intermediate their ends, said jaws having opposed jaw surfaces at one end and compression spring means

7. In a mold as described in claim 6, in which the gripped element on the slide is a dowel pin and the jaws have cooperating cam surfaces for

8. In a mold as described in claim 1, in which the gripped element on the slide is a dowel pin and the jaws have cooperating cam surfaces for yieldingly gripping and releasing said dowel pins.