EP2143528B1 - Device and method for deburring moulded parts - Google Patents

Abstract

The device (1) has a treatment chamber (2), in which ridges and/or knobs adhered by a molded part for embrittlement is inserted in a cryogenic cooling medium e.g. liquid nitrate, advanced from a supply tank (6) over a cooling medium supply unit (4). A unit for mechanical separation of the embrittled ridges or knobs from the molded part is provided in the treatment chamber. An undercooling device (11) for undercooling the cooling medium is provided in the cooling medium supply unit. A control device (25) adjusts temperature values of the undercooled cooling medium. An independent claim is also included for a method for deburring a molded part.

Description

The invention relates to a device for deburring of molded parts, in particular molded parts made of plastic, elastomers or rubber, with a treatment chamber, in the purpose of embrittlement of the molded parts adhering burrs and / or nubs introduced via a refrigerant supply from a supply tank cryogenic refrigerant, and with means for mechanically separating the embrittled burrs or nubs from the moldings in the treatment chamber.

In the production of moldings made of plastic, rubber, elastomers, etc. is usually sought to remove the remaining during the manufacturing process knobs and ridges. In the simplest case, these parts are cut off, which is laborious. Mechanical methods and devices for deburring of molded parts are also known and are used for example in the DE 195 33 392 C1 or the DE 10 2005 014 684 A1 described. In order to deburr in particular softer molded parts, the knobs and ridges are embrittled by exposure to a cryogenic refrigerant, at least superficially. The embrittled pimples or ridges are then removed mechanically in a treatment chamber. For mechanical removal suitable crushers are used, for example, the burrs and nubs are acted upon by impact material, which is registered in a designed as a rotating drum treatment chamber, or with granular blasting material which is blasted onto the moldings to be treated. In the DE 38 21 187 A1 a process for deburring rubber or plastic molded parts is described in which after cooling the elastomers to their at least superficial embrittlement deburring is to be achieved solely by the circulation of the moldings in conjunction with sharp, directed to the moldings gas jets.

A disadvantage of the aforementioned prior art is that the inlet temperature of the refrigerant entering the treatment chamber of the deburring of the pressure and the temperature of the associated with the Entgratungsanlage refrigerant tank depends. The greater the pressure in the supply tank, the higher the temperature of the refrigerant supplied to the treatment chamber. As a result, the degree of embrittlement of the knobs or burrs to be removed can only be determined in a very inaccurate manner, so that in doubt a higher amount of refrigerant is introduced into the treatment chamber than is actually necessary for the treatment. However, the increased entry of refrigerant not only leads to increased refrigerant consumption, but also to an increased thermal load of machine parts, which are subject to increased wear in this way.

The invention is therefore based on the object of specifying a possibility for deburring of molded parts, in which the entry of refrigerant is optimized and adapted to the actual requirements.

This object is achieved in that a means for subcooling the refrigerant is provided in the refrigerant supply line.

Thus, according to the invention, the refrigerant enters the treatment chamber in the liquefied, supercooled state. As "undercooled" here any condition is understood with a temperature below the corresponding boiling temperature, in which therefore the entry of a certain heat energy is required to reach the boiling point. While in deburring plants according to the prior art, a substantial portion of the nitrogen evaporates immediately upon entry into the treatment chamber and thus not only largely deprived of the embrittlement process, but contributes undesirably to the cooling of the entire Entgratungsanlage, is the liquid nitrogen in the inventive device when entering the treatment chamber preferably in the supercooled state that it still reaches the moldings to be treated in the liquid state. This minimizes nitrogen consumption and makes heat transfer more efficient.

At the same time, the device for subcooling allows the refrigerant to be introduced into the treatment chamber at a precisely defined temperature. The temperature of the refrigerant entered so no longer depends on the pressure state in the supply tank of the refrigerant. As a result, the steps required for the treatment of the molded parts can be determined accurately and in a timely manner. This speeds up the deburring process and further reduces nitrogen consumption.

An advantageous development of the invention provides that the device for supercooling comprises a flash chamber and the expansion chamber associated heat exchanger, wherein in the expansion chamber under pressure brought refrigerant expanded and the expanded medium in the heat exchanger with pressurized refrigerant in heat exchange occurs. The pressure of the supercooled refrigerant in this way corresponds at least largely to the pressure of the nitrogen in the storage tank, its temperature at least approximately that of the expanded medium. The subcooling is done in this embodiment of the invention thus without the use of external energy, but only with own medium: A portion of the refrigerant is expanded and cools down. The refrigerant cooled in this way is used to cool another part of the refrigerant, which is below the pressure prevailing in the pressure vessel and is provided for embrittlement of the moldings.

Conveniently, the temperature value of the supercooled refrigerant is adjusted or regulated by means of a suitable control device, for example by determining the pressure, to which the nitrogen introduced from the supply tank relaxes.

Preferably, the refrigerant supply line is equipped with means for directionally irradiating a molded part to be treated in the treatment chamber. The means may be, for example, a nozzle arrangement by means of which the refrigerant is applied directly to the moldings to be treated. In this way, the refrigerant is used accurately.

The object of the invention is also achieved by a method for deburring molded parts solved according to claim 5.

The refrigerant used for embrittlement is thus brought to a fixed, predetermined temperature value below the boiling point of the refrigerant and applied in the liquid state to the moldings. As a result, the temperature of the refrigerant is no longer dependent on the pressure state of the supply tank, and the time required for the embrittlement and the required dosage of the refrigerant can be reliably predicted. In addition, the refrigeration energy of the supplied refrigerant in the processing chamber is used more effectively for the embrittlement and the loss due to the evaporation of refrigerant is kept within limits.

A preferred refrigerant is liquid nitrogen. However, other refrigerants, such as carbon dioxide, may be used.

An advantageous embodiment of the invention provides that the refrigerant in the device for subcooling by at least 10 K, preferably at least 15 K below its boiling temperature-based on the pressure of the refrigerant in the Kältemittelzuführung- is cooled. For example, the nitrogen is stored in the supply tank at 5 bar in the cryogenic liquefied state and is thus at a temperature of -180 ° C before. By relaxing a portion of the liquid nitrogen to atmospheric pressure, this reaches a temperature of -196 ° C and can thus be used to cool the pressurized liquid nitrogen.

Reference to the drawings, an embodiment of the invention will be explained in more detail.

In schematic displays, the only figure ( Fig. 1 ) a device for deburring of molded parts.

The apparatus designated in its entirety by the reference numeral 1 comprises a treatment device 2 for removing cold-embrittled nubs and burrs of molded parts made of rubber, elastomers or plastic. In a treatment chamber of the treatment device 2, which is not shown here, the mold parts are exposed to a cryogenic refrigerant, wherein at least the surface of the molded parts is cooled and adhesive knobs and / or burrs are embrittled. The embrittled knobs and / or ridges are then with suitable means, such as by means of impact material, for example, after in the DE 10 2005 014 684 A1 described method removed.

As a cryogenic refrigerant nitrogen is used in the embodiment, in the context of the invention, however, other refrigerants are conceivable, for example carbon dioxide. The supply of the refrigerant to the treatment chamber of the treatment device 2 takes place in the liquid state via a pressure-resistant and thermally insulated refrigerant supply line 4. The refrigerant supply line 4 is fluidly connected to a connection piece 5 with a heat-insulated supply tank 6, stored in the nitrogen in the cryogenic liquefied state up to the level of a level 7 becomes. The supply of the liquid nitrogen to the treatment device 2 can be controlled by means of a valve 8. The nitrogen is in the interior of the supply tank 6 at its boiling point before; in the region of the connecting piece 5, this in turn is determined by the hydrostatic pressure of the liquid column standing in the interior of the supply tank 6 up to the level of the level 7. For example, at a pressure of 5 bar, the temperature of the nitrogen at the connecting piece 5 is approximately minus 180 ° C. Furthermore, in the refrigerant supply line 4, an undercooling device 11 described in greater detail below is provided, by means of which the temperature of the liquid nitrogen supplied to the treatment device 2 can be set precisely and negligibly to a value below its boiling point.

The device 11 for subcooling comprises a closed container with a lid 12 13 with thermally insulated walls. Inside the container 13, a cooling coil 14 is arranged. The cooling coil 14 is used for subcooling of liquid nitrogen from the supply tank 6, which is supplied via a thermally insulated branch line 17 of the coolant supply 4, the cooling coil 14 passes through and then the treatment device 2 is supplied. A branch line 19, which is also connected in the exemplary embodiment with the supply tank 6, opens at an expansion valve 21 into the container 13 a. The expansion valve 21 is actuated in the exemplary embodiment by a float 22 such that when falling below a predetermined height of the level 27 liquid nitrogen flows from the branch line 19 into the container 13. Instead of the float 22, however, other devices for level measurement and level control can be provided, which are operatively connected to the expansion valve 21. In the lid 12 of the container 13, an exhaust pipe 24 is provided for the discharge of gaseous nitrogen. In the exhaust pipe 24, a pressure-holding valve 25 is mounted, which keeps the pressure in the exhaust pipe 24 upstream of the pressure-holding valve 25 and thus at the same time in the container 13 to a predetermined value constant. In a simplified embodiment can be dispensed with the pressure-holding valve 25, in this case, however, the temperature of the evaporating nitrogen inside the container 13 is subjected to certain, caused by changes in atmospheric pressure fluctuations.

During operation of the device 11 for supercooling there is a bath 26 of liquid nitrogen up to the level of a certain level 27 inside the container 13. The pressure in the container 13 corresponds to the pressure set at the pressure holding valve 25 and is for example 1 bar. The pressure of the liquid nitrogen in the branch lines 17 and 19 and in the refrigerant supply line 4 approximately corresponds to that in the supply tank 6. The level of the level 27 is continuously controlled by means of float 22 and the expansion valve 21 operatively connected thereto. The temperature of the liquid nitrogen in the bath 26 is determined by the pressure at the pressure holding valve 25. In the above case of the pressure of 1 bar in the container, the temperature of the liquid nitrogen in the container is about minus 196 ° C. The top of the branch line 17 at a temperature of about minus 180 ° C brought up liquid nitrogen releases heat on its way through the cooling coil 14 to the nitrogen bath 26 in the container 13 and leaves The heat is absorbed by the liquid nitrogen in the bath 26, which is partially vaporized and discharged via line 24 and possibly supplied to a further use. After passing through the cooling coil 14, the liquid nitrogen transported to the treatment device 2 has at least approximately the temperature of the bath 26, and thus a temperature which is significantly below the boiling point of nitrogen at the pressure prevailing in the coolant supply line.

Upon entry into the warmer treatment chamber of the treatment device 2, the nitrogen is thus present in the still liquid state and can be used accurately, for example by means of suitable nozzles, for the treatment of the molded part surfaces. The constant even at varying pressure in the storage tank 6 temperature of the supplied nitrogen allows accurate dosage of the amount of nitrogen required for embrittlement.

The device 11 for subcooling works completely independent of external energy. Instead of nitrogen, other cryogenic media can be used as a refrigerant, provided that the achievable temperatures meet the requirements of embrittlement. Instead of a common source, the supply tank 6, for the lines 17 and 19 is within the scope of the invention also conceivable to supply the lines 17 and 19 from different sources and / or to feed them in particular with different media.

LIST OF REFERENCE NUMBERS

1.

contraption

Second

Behändlungseinrichtung

Third

-

4th

Refrigerant supply line

5th

spigot

6th

tank

7th

level

8th.

Valve

9th

-

10th

-

11th

Device for subcooling

12th

cover

13th

container

14th

cooling coil

15th

-

16th

-

17th

branch line

18th

-

19th

branch line

20th

-

21st

expansion valve

22nd

swimmer

23rd

-

24th

exhaust pipe

25th

Pressure holding valve

26th

bath

27th

level

Claims (8)

1. Device for deburring moulded parts, comprising a treatment chamber, into which a cryogenic coolant brought from a supply tank (6) via a coolant feed (4) is introduced for the purpose of embrittling ridges and/or nubs attached to the moulded parts, and comprising mechanical separating means for mechanically detaching the embrittled ridges or nubs from the moulded parts in the treatment chamber, characterized in that a device (11) for supercooling the coolant is provided in the coolant feed line (4).
2. Device according to Claim 1, characterized in that the device (11) for supercooling comprises an expansion chamber (13) and a heat exchanger (14) assigned to the expansion chamber (13), pressurized coolant expanding in the expansion chamber (13) and the expanded medium entering into heat exchange with pressurized coolant in the heat exchanger (14).
3. Device according to Claim 1 or 2, characterized by a control device (25) for setting the temperature value of the supercooled coolant.
4. Device according to one of the preceding claims, characterized in that the coolant supply line (4) is equipped with means for the directed blasting of a moulded part to be treated in the treatment chamber.
5. Method for deburring moulded parts, in which a cryogenic coolant is cooled to a temperature value below its boiling point in a device (11) for supercooling and, in the liquefied, supercooled state enters a treatment chamber in which the cryogenic coolant is applied to a moulded part to be treated, whereby ridges or nubs attached to the moulded part are embrittled and the embrittled ridges or nubs are subsequently detached from the moulded part by means of mechanical separating means.
6. Method according to Claim 5, characterized in that liquid nitrogen is used as the coolant.
7. Method according to Claim 6, characterized in that, when it enters the treatment chamber, the liquid nitrogen is in the supercooled state, such that it reaches the moulded part to be treated whilst still in the liquid state.
8. Method according to Claims 5 to 7, characterized in that the coolant is cooled in the device (11) for supercooling by at least 10 K, preferably at least 15 K below its boiling temperature.

Images