US2354363A - Means for heating thermoplastic materials for molding - Google Patents

Description

July 25, 1944.

A. ALVBURRY 2,354,363

MEANS FOR HEATING Tni'znmorm'iic MATERrALs FOR MOLDING '2 Sheets-Sheet 2 Filed April 23, 1943 [rm enter. v Ar/Aur'A.Burr

Patented July 25,

UNITED STATES PATENT OFFICE MEANS FOR HEATING THERMOPLASTIC MATERIALS FOR MOLDING Arthur A. Barry, Toronto, Ontario, Canada Application April 23, 1943, Serial No. 484,296

8 Claims. (Cl. 1830) This invention relates to improvements in the construction of the means'for heating thermoplastic material as it is fed to the molds or dies,

and the principal object of the invention is to provide an apparatus capable of operation free from leakage of the heating medium under excessive temperatures and pressures and to devise a structure which may be manufactured at reasonably low cost and which will ,be.simple and easy to assemble.

The principal feature of the invention consists in the novel construction and arrangement of a hollow core to be supported within a cylinder through which the thermo-plastic material is forced which is surrounded by a sealed jacketprovided with an immersion electric heating unit arranged at the bottom thereof below the bottom of the cylinder to generate steam and, eflect the continuous flow thereof around the cylinder to create and maintain a substantially uniform temperature surrounding the cylinder to plastify the contents thereof, whereby communication between the steam jacket surrounding the cylinder and the interior of the core is maintained through ducts formed in the cylinder registering with ducts formed in the core and communicating with the central chamber thereof, the sealing of the juncture of the ducts of the core and the cylinder body being effected with compression sealing. In the accompanying drawings I Figure 1 is a longitudinal mid-sectional view of a thermo-plastic heating cylinder constructed in accordance with this invention, the section being made on the line l-l of Figure 2.

Figure 2 is a transverse section of the device taken through the line 2'2 of Figure .1.

hollow steam-heated core is disclosed in my 00- pending application No. 308,549, of December 11, 1939, now U. S. Patent No. 2,319,439, dated May 18, 1943.

Certain classes of thermo-plastic material and the molding of certain articles from 'thermoplastic material require extremely high-temperatures and pressures. and the present invention has been devised in order to obviate leakage of the heat-transmitting fluid in the form of high pressure steam.

In the construction herein illustrated the cylinder I, in which the plastic material. is confined,

'is surrounded by a cylindrical jacket 2 which isspaced from the outer surface of the cylinder and is provided with intumed end flanges 3 and l which form a sealed joint with the outer surface Figure 3 is an elevational view of the discharge nozzle end of the device partly broken away.

Figure 4 is a longitudinal sectional view of the nozzle end of the cylinder taken on the line 4-4 of Figure 2.

Figure 5 is an eievational detail of the inward end of the core.

Figure 6 is a transverse section on the line 6-0 of Figure 1. 1

In my United States Patent 2,115,940, dated May 3, 1938, I disclosed a Plastic injection device in the form of a cylinder having a discharge orifice and provided with pressure. means for ejecting the cylinder contents with the cylinder surrounded by a sealed jacket spaced therefrom and in which an immersion electric heating unit was arranged at the bottom of the jacket below the bottom of the cylinder, said jacket containing a body of water surrounding the heater whereby steam eter of the cylinder.

of the cylinder wall. The jacket and the cylinder are assembled with a tight driving fit and, being both constructed of metal of the same coefficient of .expansion, a-pressure tight joint is ef'-' fected as each of the flanged ends of the jacket are under extremely high pressures and tem peratures. v

The end of the jacket remote from the discharge end of the cylinder is provided with a transverse chamber 5 which extends below, the

bottom of the interior of the jacket 2 and supported therein is an electric heating element 6 which is immersed in a body of water 1. When current is applied to the heating element 6 steam is generated and this circulates around the perimeter of the cylinder i and maintains a constant application of temperature to' the entire perim- It will be understood that owing to the ex- .treme elasticity of steam the instant that heat is absorbed therefrom it willbe replaced by the constantly circulating steam body and condensation will immediately return to the heating chamber 5. This principle has been, effectively proven in extensive commercial use of heaters made in accordance with my Patent Nor 2,115,940.

It has been found expedient to provide a dome cess through the orifice ll.

plugs 28.

to the'steam chamber and this is arranged in the form of a recess 8 formed in the topside of the jacket 2, preferably above the chamber I, and a suitable gauge I is connected with this re- An orifice II is provided for the purpose of inserting .water into the device and this is closed by a suitable plug it.

In the bottom of the chamber are arranged a pair of obliquely disposed orifices l3 and H.

These are closed by suitable'safety fuse plugs II which may be an'anged to blow at any desired maximum pressure.

At the nozzle or discharge end of the the cylinder wall is drilled inwardly from the ends to form a plurality of ducts l8 which connect with radialducts H which open through the outer wall of the, cylinder into the space enclosed by the jacket 2 so that a plurality of ducts commuto the end of the cylinder. The end of each of the ducts II is counterbored,. preferably. with a taper counterbore II and into each of these counterbores is fitted a compression seal is in the form of a ferrule of copper or other suitable ductile metal.

The end face of the cylinder is formed with a counterbore 20. .A circular head 2|, adapted to fit snugly into the counterbored end of the cylinder l, is provided with a cylindrical core extension '22, 'the outer perimeter of which is spaced from the inner wall of the cylinder I. is preferably pointed at its inner end to direct the thermo-plastic material outwardly between the outer wall of the core and the inner wall of the cylinder. The core is preferably supported adiacent to its inner 'end by suitable fins 23.

The face of the head which engages the counterbored end face of the cylinder! is formed.

This core asisascs.

cylinder nicate with the steam jacket and lead outwardly lating steam through this wall to plastify the material as it is forced through the annular passage between the core and the cylinder wall.

The head II is formed to fit snugly into the counterbores of the end of the cylinders and it is secured firmly in position by a plurality of cap screws 33 which are threaded into threaded holes 34 arranged in the end of the cylinder and spaced between the ducts II.

It will.be readily appreciated that the closefitting surfaces of the head I and cylinder ends will prevent the escape of the thermo-plastic material that is being forced through the cylinder and the compression seals it may be compressed by the tension of the cap screws 33 tmhold any required pressure of steam that may be used in sealing the ducts communication between the steam jacket and the interior of the core.

with tapered counterbored recesses '24 which register with the counterbored recesses It in the end of the cylinder and which receive the projecting ends of the compression seal members I! when the head is placed in position. The compression seal members are bored and communicate with holes 25 which are aligned with the ducts l6 by the compression sealing members.

Diagonal ducts flare bored in thehead If to communicate with the outward ends of .the holes 25 and open inwardly into the hollow interior 21 of the'core 22, the outer ends of -'the ducts 2| beyond the holes ll are sealed with suitable From this description it will be understood that a plurality of ducts form communicating passages with the steam jacket surrounding the cylinder and the centre of the core 22,- and steam entering the chamber 21 of the core circulates freely and condensation will be carried out through the lower duct into the bottom of the steam jacket to find its way to the steam-generating chamber described.

The head :1 is provided with a t 'ed coun- It will be understood from thisdescription that the structure of the device is simple and it may be manufactured'very readily at very moderate cost.

When the cylinder and head are machined and readyfor assembly the conical compression seals are simply inserted in the counterbored recesses,

the head and cylinder are placed together-and the cap screws are drawn up tight to complete theseal concurrently of the cylinder and the steam jacket and p ssages.

With a device such as described extremely high temperatures may be applied to plastify the thermo-plastic material without danger of burning the material and a constant anduniform condition of molding may be maintained.

It is found desirable to provide for the release of air which may be trapped within the steam chambers. and I provide a pipe 35, preferably inserted into the dome 8 and provide same with a suitable valve (not shown) to facilitate such removal. v

What I claim as my invention is:

l. A means-for heating thermo-plastic materials for molding, comprising a cylinder having an open end surrounded by a steam jacket, said cylinder havin ducts formed therein communicating with the steam jacket and leading to an end surface, a head closing the open end-oi the cylinder and having a hollow core extending terbore 2! which has a central conicalprojec- 'tion 3. and a plurality of holes 3| are bored through the head portion in groups arranged between the ducts It and leading from me annular space between the inner cylinder wall and the external wall of the core 22. These holes are shown in the form of groups of tapered holes but they may constitute open passages and they are aligned with the tapering wall of the conical projection 130 so that the thermo-plastic material which .is forced through the cylinder fiows out through the tapered holes or passages and around the conical projection ll; A suitable nozale I! is 18 into and spaced from the cylinder wall, said head having ducts communicating with the ducts in the cylinder andleading into the hollow core. and means for pressure sealing the juncture of the'ducts of said cylinder with the ducts of said head. I

2. A means for heating thermo-plastic materials for molding, comprising a cylinder having an open end and surrounded with a steam'iacket and having ducts formed therein leading from the steam jacket to the open end of the cylinder,

a head abutting the open end of the cylinder and having a hollow core extending into the cylinder, ducts in the head aligned with the ducts in thecylinder wall and leading inwardly to the hollow core, the adjacent meeting end'sof saidcylinderand head ductsbeing counterbored, per- I 7 3,854,868 forated compressible sealing members seated insaid counter-bores and joining the ducts, and

' means for drawing the head into sealed contact with the end of the cylinder.

3. Adevice as claimed inclaim .2 in which the co'unterbores in the adjacent meeting ends of the head and cylinder ducts'are tapered, the compressible sealing members being in the form of tapered metallic ferrules inserted in said counterbores and pressed into sealing engagement therewith. 4. A device as claimed in claim 1 in which passages leading from the interior of the cylinder extend through the head between the ducts connecting the steam jacket with thehollow core,

said passages leading to a discharge orifice in the head. Y

5. A device as claimed in claim 1 in which the head is formed with a counter-bored recess in its outer side provided with. a central conical extension and passages lead inwardly from the base of said conical extension through the head and spaced therefrom, I ducts communicating with the hollow interioroi the core and'leading outwardly to align with the ducts extending from the steam jacket through the end of the cylinder, the interior oi the core being in cylindrical form and having conical ends and the exterior ends of the core being conical, means for compression sealing the adjoining ducts of the cylinder and head, and means forv securing said head in compression sealing contact, said head having discharge orifices leading from the interiorof the cylinder.

'7. Means for heating theme-plastic materials I formolding,..comprising a cylinder having 'an open end and a steam Jacket therearound and having ducts arranged at the top and bottom leading from the steam jacket to an end surface of the cylinder, a head engaging in sealing steam jacket through'the open end of the cylinder, a head closing the end of the cylinder hav- .iack'et. ing a hollow core extending into the cylinder contact with the open end ofthe cylinder and having a reduced core extension projecting into the cylinder'and spaced from the cylinder and having a pointed end, ducts formed in the head registering with the ducts in the cylinder and leading to the hollow core, means for pressure sealing the adjacent ends of the cylinder and head ducts, cap screws threaded into' the cylinder extending through the head and clamping the head to the cylinder end in sealed contact,-

" and discharge passages arranged in said head leading to a common discharge orifice from the interior of the cylinder.

8. A device as claimed in claim 1 having an air release duct leading from the top of the steam ARTHUR A. HURRY.

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