Device for demolding negatives in thermoplastic injection molds

Abstract

A device for demolding negatives in thermoplastic injection molds includes an ejector which comprises an ejector profile for the fastening thereof to an ejector plate and a figure insert with a profile that is complementary to a piece to be molded. The ejector further comprises a flexible element arranged between the ejector profile and the figure insert which pushes the figure insert in order to demold the negative by an angular displacement and stretches the figure insert so as to return the ejector to the injection position thereof. The device eliminates the need for molding sliders which are costly as well as the need for a machining process for the installation thereof.

Claims

1. A device for demolding one or more negatives in thermoplastic injection molds, said device including an ejector (3) that comprises: an ejector profile (5) for fastening thereof to an ejector plate (2); and a figure insert (6) with a profile that is complementary to a piece (4) to be molded, said piece (4) having said one or more negatives, wherein said ejector (3) also comprises a flexible element (7) arranged between said ejector profile (5) and said figure insert (6), which pushes said figure insert (6) in order to demold said one or more negatives by means of an angular displacement, said ejector (3) thereafter returning to an injection position thereof, and wherein said flexible element (7) is a helical spring that is not compressible or extendable.

2. The device for demolding one or more negatives in thermoplastic injection molds according to claim 1, wherein said helical spring is combined with a cable, forming a single flexible element (7).

3. The device for demolding one or more negatives in thermoplastic injection molds according to claim 1, wherein said flexible element (7) is joined to said figure insert (6) and to said ejector profile (5) by means of a connection portion (8).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For the purpose of helping to make the foregoing description more readily understandable, it is accompanied by a set of drawings which, schematically and by way of illustration and not limitation, represent an embodiment.

(2) FIG. 1 is a view of the components of the device for demolding negatives in thermoplastic injection molds according to the present invention;

(3) FIG. 2 is a cross-section elevation view of a mold that comprises the device for demolding negatives in thermoplastic injection molds according to the present invention, in its position of injection on the left-hand side and in its position of ejection on the right-hand side; and

(4) FIG. 3 is an elevation view of the detail of the area of the figure insert and the piece during the demolding thereof.

DESCRIPTION OF A PREFERRED EMBODIMENT

(5) Firstly, it must be stated that the device in accordance with the present invention is used for demolding negatives that are normally considered small, meaning with dimensions smaller than 3 mm in the negative area thereof.

(6) FIG. 1 shows the components that make up the device in accordance with the present invention, referred to in its entirety as an ejector and identified with the reference number 3, in order to facilitate the description.

(7) This ejector comprises an ejector profile 5 fixed to an ejector plate 2 of the mold 1, as can be seen in FIG. 2, a figure insert 6 that has a form that is complementary to the piece 4 to be molded, and a flexible element 7.

(8) According to the embodiment shown, said flexible elements 7 is a helical spring complemented with an integral cable, in which the coils thereof are in contact with each other at least at one point. In other words, said element is not compressible or extendable, but rather deforms to adapt to the form of the housing of the mold through which it moves, as will be described below.

(9) The function of said flexible element 7 is to push said figure insert 6 in order to demold the negative by means of angular displacement and stretch said figure insert 6 so as to return the ejector 3 to the injection position thereof.

(10) To facilitate this pushing and stretching action of the flexible element 7, the same is joined to the ejector profile 5 and to the figure insert 6 by means of a threaded, welded or fitted connection portion 8, which converts it to a single demolding element, as shown in FIG. 1.

(11) FIG. 2 shows a mold 1 that includes the device for demolding negatives according to the present invention.

(12) In a conventional way, said mold comprises an ejector plate 2, to which the ejector 3 is attached.

(13) This ejector 3 is housed in an angular housing machined in the punch of the mold 1, and as can be seen in FIG. 2, to allow for the demolding of the pieces with a negative configuration.

(14) Said housing has a polygonal cross section, for example, square, in other words, non-circular, to prevent the rotation of the figure insert 6 in the inside thereof. To this end, the figure insert 6 also defines a corresponding polygonal cross section.

(15) On the left-hand side of FIG. 2, the mold 1 is shown in its injection position, while on the right-hand side the mold is shown in its ejection position.

(16) In the punch of the mold 1 the trajectory of the movement of the ejector device is machined, which adapts its path thanks to the flexible element 7, and on the one hand, the profile of the figure follows the trajectory machined in the punch of the mold, while the other connection fitted in the ejector plate will follow the trajectory of the ejector plates.

(17) It is important to highlight that the system described is perfectly adapted to for the demolding of small elements, mainly by facilitating the machining and installation thereof, but that its use is not suitable for large demolding, by the simple fact that in all cases it is a single deformable element that is neither compressible nor extendable, and, therefore, one part of the same can follow a vertical path, while the other part can follow an inclined path in relation to the former, and thus the vertical paths are different, although on a small scale, and always within the tolerances of the operations within the sector. FIG. 3 graphically shows the demolding effect

(18) The demolding process by means of the device in accordance with the present invention is described below.

(19) As can be seen on the left-hand side of FIG. 2, in this position the injection of the mold 1 is carried out, and the flexible element 7 has a lower vertical portion and an upper inclined portion. It must be stated that in this embodiment the coils of the helical spring are in contact with each other in their entirety with the exception of in the transition zone from the lower vertical portion to the upper inclined portion, where the coils are in contact at one point.

(20) When one wants to eject or demold the piece, the ejector plate 2 moves vertically upwards. This movement also causes the sliding of the flexible element 7 upwards, also defining a lower vertical portion and an upper inclined portion in the same. As can be seen in FIG. 2, said transition zone (indicated by the letter Z in FIG. 2) is always at the same height with respect to the mold 1.

(21) The push that the flexible element 7 exerts on the figure insert 6 causes the movement of the demolding that is shown in FIG. 3, which forms a right angle with respect to the direction of the movement of the ejector 3, in other words, with respect to the longitudinal axis of the figure insert 6.

(22) Once the piece 4 is demolded, the ejector plate 2 will return to its injection position, such that the flexible element 7 stretches the figure insert 6 to its injection position, shown on the left-hand side of FIG. 2.

(23) Despite the fact that reference has been made to a specific embodiment of the invention, it is evident for a person skilled in the art that numerous variations and changes may be made to the device described, and that all the aforementioned details may be substituted by other technically equivalent ones, without detracting from the scope of protection defined by the attached claims.