GB1573352A

GB1573352A - Deflashing and debonding method and apparatus

Info

Publication number: GB1573352A
Application number: GB3797777A
Authority: GB
Original assignee: BOC Ltd Australia
Current assignee: BOC Ltd Australia
Priority date: 1977-09-12
Filing date: 1977-09-12
Publication date: 1980-08-20
Also published as: AU3972478A; AU523942B2

Description

(54) DEFLASHING AND DEBONDING METHOD AND APPARATUS (71) We, BOC LIMITED, an English company of Hammersmith House, London W6 9DX, England, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to method and apparatus for deflashing and debonding.

It is current commercial practice to remove the flash from, for example, moulded articles of elastomeric material, such as rubber, or of plastics material, or from die-cast articles in a rotary drum, introducing liquid nitrogen in the drum and rotating the drum.

The liquid nitrogen has the effect of rendering the flash brittle. The tumbling action caused by rotating the drum causes the articles to endure repeated impacts. The effect of the impacts is to cause the flash to be broken off from the articles. After the drum has been rotated for a chosen period of time, it may be brought to a halt and the articles and separated flash may then be unloaded from the drum. It is also known to debond articles of composite material, for example, composite rubber-metal articles, by analogous methods.

According to the present invention there is provided a method of deflashing articles of material which is rendered relatively brittle by a reduction in its temperature to below ambient temperature, which method comprises introducing articles to be deflashed through an inlet into an elongate rotary member defining a downwardly inclined passage, rotating said member so as to cause the articles to tumble pass along the passage to an outlet, and introducing into the passage and into heat exchange relationship with the articles a coolant having a temperature sufficiently below ambient to render the articles sufficiently brittle that the impacts caused by the tumbling action of the articles as they pass along the passage effect or assist in effecting deflashing of the articles.

The invention also provides a method of debonding pieces or articles of composite material, one component of the material being rendered brittle by a reduction in its temperature to below ambient temperature, which method comprises introducing articles or pieces of the composite material to be debonded through an inlet into an elongate rotary member defining a downwardly inclined passage, rotating said member so as to cause the articles or pieces to tumble and to pass along the passage to an outlet, and introducing into the passage and into heat exchange relationship with the articles or pieces a coolant having a temperature sufficiently below ambient to render the articles or pieces sufficiently brittle that the impact caused by the tumbling action of the articles or pieces as they pass along the passage effect or assist in effecting debonding of the articles or pieces.

The method of deflashing according to the present invention is capable of being operated continuously. So is the method of debonding according to the present invention. In this respect the methods according to the present invention are an improvement over the hitherto described known processes which are capable only of being operated discontinuously as batch processes.

The invention also provides apparatus arranged to perform the method of deflashing or the method of debonding according to the present invention, said apparatus comprising an elongate rotatory member defining a downwardly inclined passage having at opposite ends thereof an inlet and an outlet for articles to be debonded or deflashed or for pieces of composite material to be debonded, means for rotating the elongate member and means for introducing a coolant into the passage.

The apparatus according to the present invention is capable of being operated con tinuously.

The passage is preferably inclined at an angle of 10 or less to the horizontal. More preferably the angle of inclination is 5 or less to the horizontal. Such a relatively small inclination assists in preventing axial 'slippage' of the contents, which in effect would reduce considerably the cooling time, and also provides a relatively long residence time for the contents in the passage. The passage may be generally circular in cross-section.

Alternatively, it may be square, rectangular or polygonal in cross-section. Passages of polygonal cross-section assists in setting up the tumbling action.

The choice of angle of inclination of the passage, the speed of rotation of the elongate member and the internal diameter of the passage determine the rate at which articles or pieces in the passage progress down the passage. The length of the passage will then dictate the residence time of the articles or pieces in the passage. Alternatively, given a passage of fixed length and diameter, the residence time is controlled by varying the angle of inclination and/or the speed of rotation of the elongate member. In order to give complete, or nearly complete deflashing, this residence time should preferably be at least ten minutes.

For a fixed internal diameter, the percentage of the cross-sectional area of the passage occupied by the contents will, in conjunction with the rate of travel of the contents, dictate the residence time of the contents in the tunnel. This percentage loading should preferably be maintained within the range 5-25% of passage cross-sectional area. Outside this range, the efficiency of deflashing could be impaired, and the motion of the contents will be less controllable.

Preferably, the elongate member is rotated at 15 to 45 revolutions per minute.

If desired, the passage may be provided with a 'dam' member which reduces it crosssection and thereby assisis in increasing the residence time. By causing the contents to pile up on its upstream side the darn also assists the heat transfer between the contents and the cold gas by increasing the exposed surface area.

If desired, the passage may be provided with means to assist the tumbling action. For example, buckets or lifters may be supported within the tunnel. The buckets or lifters can be flat plates or can be scoop-shaped. In operation they carry material upwards and allo > . . o tumble through a greater height than it mould otherwise. The shape, size and sitie of each lifter or bucket and its axial ength would determine the amount of contents it carries, in use and the distance through which it tumbles. Lifters or buckets also offer the advantage of assisting heat transfer between the articles or pieces and cold gas evaporating from liquefied gas introduced into the passage.

On some occasions, it may be that the tumbling action in itself will not be effective to enable complete deflashing to be carried out. In such instances, various additional means may be provided to facilitate deflashing or debonding. For example, impact members such as chains or cables suspended at intervals along the passage may be provided. Such chains or cables would also offer the advantage of assisting in the cooling of the articles or pieces since they would first become at least in part embedded in the articles or pieces thereby absorbing their heat and half a revolution later they would be hanging at least in part in the gas space thereby contacting cold gas and hence being reduced in temperature.

Another means for assisting the tumbling action to effect debonding or deflashing is to include in the passage a relatively hard particulate material, for example, ceramic chips.

The impact of such chips against the articles or pieces being deflashed or debonded will assist to break off the flash or separate one component of a composition material from another. However, means will need to be provided for separating the relatively hard particulate material from the deflashed articles or debonded articles or pieces of material at or downstream of the outlet.

Another means for assisting the tumbling action to effect debonding or deflashing is to arrange for the passage to have an inlet through which shot may be blasted at the articles or pieces being debonded or deflashed. If such means are provided it will be desirable to provide a device at or downstream of the outlet for separating the shot from the deflashed articles or debonded articles or pieces.

The apparatus according to the present invention preferably also includes means for feeding the articles or pieces into the inlet at a controlled rate. For example, the means may include suitable flaps or valves, preferably automatically controlled, and operable to feed material into the tunnel at a controlled rate. Such flaps or valves are also preferably designed so as to prevent unwanted ingress of air or loss of cold gas from the passage. Analogously the outlet of the passage preferably has similar means for controlling the flow of material out of the passage and for preventing unwanted ingress of air or loss of cold gas from the passage.

The elongate member may be made of materials conventionally used for making devices required to operate at below ambient temperature. For example, it may be made of stainless steel. Any convenient means for rotating the elongate member may be employed.

Preferably, the coolant is contacted directly with the articles to be deflashed or the articles or pieces to be debonded. It is possible, however, to arrange for a coolant to be conducted through heat exchange pipes within the passage so as to cool the air in the gas space in the passage. This, however, is a relatively inefficient method of reducing the temperature of the material in the passage and is not recommended. The coolant is preferably a liquefied gas. The preferred liquefied gas is liquid nitrogen. This coolant will be suitable for most, if not all, deflashing or debonding applications. However, other liquefied gases such as liquid argon, liquid helium or liquefied natural gas may be used.

Liquid carbon dioxide may on some occasions be used; but using this liquefied gas it is sometimes difficult or impossible to achieve the relatively low temperature needed to embrittle, say, rubber.

The liquefied gas, or its vapour, (or both) is (or are) preferably brought into direct contact with the material in the passage. The liquefied gas may, for example, be sprayed into the passage. Alternatively, or in addition, the passage may have a section of wider diameter and walls capable of holding a volume of liquid and the liquefied gas may be supplied to such wider section such that in use of the passage the articles to be deflashed or the articles or pieces of material to be debonded may be advanced through the volume of liquefied gas. Means for spraying liquefied gas into the passage may be positioned anywhere along its length. Typically, the spray means may be mounted at or near its inlet end. Such an arrangement makes it possible to make good use of the evaporating liquefied gas as a coolant and to avoid unnecessary difficulties in mounting the spray means within the passage.

The passage preferably has an outlet for evaporated gas spaced well apart from the means for spraying liquefied gas into the passage. The outlet is therefore preferably located at or near the outlet end of the passage. This outlet is desirably connected to a fan or blower. In operation the fan or blower may be used to create a flow of evaporated gas along the passage above the articles to be deflashed or the articles or pieces of material to be debonded, the flow being in the same direction as that of the articles or pieces.

The method and apparatus according to the present invention will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 is a schematic side view of apparatus according to the invention.

Figure 2 is a schematic cross-sectional view of the apparatus shown in Figure 1; Figure 3 is a schematic side view of a part of an alternative form of passage to that shown in Figure 1; Figures 4 to 6 are schematic crosssectional views of further alternative embodiments of the passage.

Referring to Figure 1 of the drawings, deflashing or debonding apparatus includes a tunnel 1 inclined at an angle to the horizontal. The tunnel 1 is mounted within support rings 2 which ride on rollers 3. In Figure 2 is shown a cross-section of the tunnel in the region of a support ring. The means for rotating the tunnel are not shown. It is conceivable that the tunnel could run directly on the rollers. However, rotational drive to the tunnel is preferably facilitated by a frictional drive through one or more rollers, by geared drive through the rollers or by chain drive through a sprocket ring mounted on the tunnel. The tunnel may be rotated in either sense (i.e. clockwise or anti-clockwise). At the upper, inlet end of the tunnel 1 is located an inlet chute 4. A suitable sealing ring (not shown) is engaged between the lower end (as shown) of the inlet chute 4 and the upper end of the tunnel 1. The inlet chute 4 has automatically controlled flaps 5 which are operable to define an inlet of chosen size into the tunnel 1. It is thus possible to regulate the flow of articles to be debonded or deflashed into the tunnel 1. The flaps 5 are arranged so as to keep down or prevent unwanted ingress of air or loss of cold gas from the tunnel 1.

The tunnel 1 defines a passage 10 of circular cross-section. The passage 10 and the tunnel 1 are inclined from inlet to outlet in a downward direction at a slight angle to the horizontal. Connected to the lower or outlet end end of the passage 10 is an end member 12 defining at its lower end an outlet chute 13.

An annular sealing ring (not shown) is engaged between the end of the tunnel 1 and the end member 12. The outlet chute 13 has automatically controlled flaps 14 similar to the flaps 5. Thus debonded or deflashed articles may be discharged from the tunnel 1 at a controlled rate. A spray header 17 is mounted in the gas space near the inlet of the tunnel 1. The spray header 17 has several spray nozzles 18 which direct into the interior of the passage 10 sprays of liquid nitrogen. The liquid nitrogen is supplied from a vacuum insulated evaporator 16 via a pipeline 19. If desired, a temperature sensor (not shown) may be located, for example, in the gas space at or near the outlet end of the passage 11 and the sensed temperature is ued to control a solenoid valve (not shown) in the pipeline 19. By this means, liquid nitrogen may be injected into the passage 10 only when the sensed temperature is above a chosen value. By this means, it is possible to limit the amount of liquid nitrogen that is consumed during operation of the apparatus.

Evaporated nitrogen is in operation of the tunnel 1 drawn along the passage 10 by means of a fan 21 in communication with an outlet 20 forming part of the end member 12.

By rotating the tunnel 1 and feeding articles to be deflashed or debonded into the tunnel through the inlet chute 4 the articles will be caused to advance along the passage 10 being tumbled as they do so. The tumbling causes impact of the articles against each other and the walls of the tunnel 1 thereby effecting deflashing of the articles. It is to be appreciated that such deflashing is made possible partly by the effect that the cold nitrogen has on the articles. This is to render them brittle. If, instead of being deflashed, composite articles are to be debonded the tumbling action is effected to separate, say, an embrittled rubber surface from a metal article. Referring now to Figure 3, a portion of the tunnel 1 has a widened cross-section as indicated by the reference number 30. A volume of liquid nitrogen 31 is maintained in the widened section 30. In operation, articles to be deflashed or debonded are advanced through the liquid nitrogen so as to render the flash or the part of the composite parti cles to be debonded, as the case may be, brittle.

Referring to Figure 4, lifters are spaced apart along the length of the passage 10. The action of the lifters is to collect some of the articles to be deflashed or debonded when the collecting surface is facing upwards and to let such collected articles fall under gravity when the collecting surface of the lifters starts to face downwards as the tunnel is rotated. This helps to enhance the tumbling action and thereby facilitates debonding or deflashing as the case may be.

Referring to Figure 5, it will be seen that the tunnel 1 does not have a wall of circular cross-section as shown in Figure 2 but instead is of octagonal cross-section. Such a cross section facilitates the coupling action. Refer ring to Figure 6. chains 62 are connected to the wall of the tunnel 1 defining the passage 10. These chains are provided at spaced apart intervals along the entire length of the panel. Impact of the articles to be deflashed or debonded against the chains in operation of the apparatus causes impacts which facili tate the deflashing or debonding auction, as the case may be. In addition, the chains facili tate heat transfer between the relatively warm articles and cold nitrogen vapour.

Referring again to Figure 1, if desired the cold gas exhausted from the fan 21 may be recirculated to the hopper 4 so as to precool incoming components.

Other constructions of tunnel are also possible. For example, coolant, e.g. liquefied gas such as liquid nitrogen, may be intro educed, for example through a sprayer, at or rWlS the bottom end of the tunnel, and ted coolant may be caused to flow in te direction to the contents of the ,eration of a fan or blower in ;nn xvith tho tnn pnrl nf thsz nel. If desired, in this and other embodiments of the tunnel, a bath of liquefied gas may be employed instead of the spray.

Another optional constructional feature of the tunnel is for it to be of non-uniformal cross-sectional area along its length. For example, a relatively narrow cooling region may be provided upstream (with respect to the flow of the solid contents) of a wider deflashing or debonding region. Liquid nitrogen, for example, may be introduced, typically by spraying into the cooling region.

WHAT WE CLAIM IS: 1. A method of deflashing articles of material which is rendered relatively brittle by a reduction in its temperature to below ambient temperature, which method comprises introducing articles to be deflashed through an inlet into an elongate rotary member defining a downwardly inclined passage, rotating said member so as to cause the articles to tumble and pass along the passage to an outlet, and introducing into the passage and into heat exchange relationship with the articles a coolant having a temperature sufficiently below ambient to render the articles sufficiently brittle that the impacts caused by the tumbling action of the articles as they pass along the passage effect or assist in effecting deflashing of the articles.

2. A method of debonding pieces or articles of composite material, one component of the material being rendered brittle by a reduction in its temperature to below ambient temperature, which method comprises introducing articles or pieces of the composite material to be debonded into an elongate rotary member defining a downwardly inclined passage, rotating said member so as to cause the articles or pieces to tumble and pass along the passage to an outlet, and introducing into the passage and into heat exchange relationship with the articles or pieces a coolant having a temperature sufficiently below ambient to render the articles or pieces sufficiently brittle that the impacts caused by the tumbling action of the articles or pieces as they pass along the passage effect or assist in effecting debonding of the articles or pieces.

3. A method as claimed in claim 1 or claim 2, in which the passage is inclined to the horizontal at an angle of 10 or less.

4. A method as claimed in claim 3, in which the angle is 5 or less.

5. A method as claimed in any one of the preceding claims, in which the passage is generally circular in cross-section.

6. A method as claimed in any one of claims 1 to 4, in which the passage is square, rectangular or polygonal in cross-section.

7. A method as claimed in any one of the preceding claims, in which the residence time of the articles or pieces in the tunnel is at least I m;nntpr

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

By rotating the tunnel 1 and feeding articles to be deflashed or debonded into the tunnel through the inlet chute 4 the articles will be caused to advance along the passage

10 being tumbled as they do so. The tumbling causes impact of the articles against each other and the walls of the tunnel 1 thereby effecting deflashing of the articles. It is to be appreciated that such deflashing is made possible partly by the effect that the cold nitrogen has on the articles. This is to render them brittle. If, instead of being deflashed, composite articles are to be debonded the tumbling action is effected to separate, say, an embrittled rubber surface from a metal article. Referring now to Figure 3, a portion of the tunnel 1 has a widened cross-section as indicated by the reference number 30. A volume of liquid nitrogen 31 is maintained in the widened section 30. In operation, articles to be deflashed or debonded are advanced through the liquid nitrogen so as to render the flash or the part of the composite parti cles to be debonded, as the case may be, brittle.

Referring to Figure 4, lifters are spaced apart along the length of the passage 10. The action of the lifters is to collect some of the articles to be deflashed or debonded when the collecting surface is facing upwards and to let such collected articles fall under gravity when the collecting surface of the lifters starts to face downwards as the tunnel is rotated. This helps to enhance the tumbling action and thereby facilitates debonding or deflashing as the case may be.

Referring to Figure 5, it will be seen that the tunnel 1 does not have a wall of circular cross-section as shown in Figure 2 but instead is of octagonal cross-section. Such a cross section facilitates the coupling action. Refer ring to Figure 6. chains 62 are connected to the wall of the tunnel 1 defining the passage 10. These chains are provided at spaced apart intervals along the entire length of the panel. Impact of the articles to be deflashed or debonded against the chains in operation of the apparatus causes impacts which facili tate the deflashing or debonding auction, as the case may be. In addition, the chains facili tate heat transfer between the relatively warm articles and cold nitrogen vapour.

Referring again to Figure 1, if desired the cold gas exhausted from the fan 21 may be recirculated to the hopper 4 so as to precool incoming components.

Other constructions of tunnel are also possible. For example, coolant, e.g. liquefied gas such as liquid nitrogen, may be intro educed, for example through a sprayer, at or rWlS the bottom end of the tunnel, and ted coolant may be caused to flow in te direction to the contents of the ,eration of a fan or blower in ;nn xvith tho tnn pnrl nf thsz nel. If desired, in this and other embodiments of the tunnel, a bath of liquefied gas may be employed instead of the spray.

Another optional constructional feature of the tunnel is for it to be of non-uniformal cross-sectional area along its length. For example, a relatively narrow cooling region may be provided upstream (with respect to the flow of the solid contents) of a wider deflashing or debonding region. Liquid nitrogen, for example, may be introduced, typically by spraying into the cooling region.

WHAT WE CLAIM IS: 1. A method of deflashing articles of material which is rendered relatively brittle by a reduction in its temperature to below ambient temperature, which method comprises introducing articles to be deflashed through an inlet into an elongate rotary member defining a downwardly inclined passage, rotating said member so as to cause the articles to tumble and pass along the passage to an outlet, and introducing into the passage and into heat exchange relationship with the articles a coolant having a temperature sufficiently below ambient to render the articles sufficiently brittle that the impacts caused by the tumbling action of the articles as they pass along the passage effect or assist in effecting deflashing of the articles.
2. A method of debonding pieces or articles of composite material, one component of the material being rendered brittle by a reduction in its temperature to below ambient temperature, which method comprises introducing articles or pieces of the composite material to be debonded into an elongate rotary member defining a downwardly inclined passage, rotating said member so as to cause the articles or pieces to tumble and pass along the passage to an outlet, and introducing into the passage and into heat exchange relationship with the articles or pieces a coolant having a temperature sufficiently below ambient to render the articles or pieces sufficiently brittle that the impacts caused by the tumbling action of the articles or pieces as they pass along the passage effect or assist in effecting debonding of the articles or pieces.
3. A method as claimed in claim 1 or claim 2, in which the passage is inclined to the horizontal at an angle of 10 or less.
4. A method as claimed in claim 3, in which the angle is 5 or less.
5. A method as claimed in any one of the preceding claims, in which the passage is generally circular in cross-section.
6. A method as claimed in any one of claims 1 to 4, in which the passage is square, rectangular or polygonal in cross-section.
7. A method as claimed in any one of the preceding claims, in which the residence time of the articles or pieces in the tunnel is at least I m;nntpr
8. A method as claimed in any one of the preceding claims, in which the percentage of the cross-sectional area of the passage occupied by the pieces or articles is in the range 5 to 25 % of the total cross-section area of the passage.
9. A method as claimed in any one of the preceding claims in which the elongate member is rotated at 15 to 45 revolutions per minute.
10. A method as claimed in any one of the preceding claims, in which the passage is provided with a dam member which reduces its cross-section.
11. A method as claimed in any one of the preceding claims, in which chains or cables are suspended at intervals along the passage so as to facilitate debonding or deflashing.
12. A method as claimed in any one of the preceding claims, in which pieces of hard material are introduced into the passage so as to facilitate debonding or deflashing.
13. A method as claimed in any one of the preceding claims, in which the material to be debonded or deflashed is shot blasted as it passes through the passage.
14. A method as claimed in any one of the preceding claims, in which the coolant is liquefied gas.
15. A method as claimed in claim 14, in which the liquefied gas is liquid nitrogen.
16. A method as claimed in claim 14 or claim 15, in which the liquefied gas is sprayed into the passage.
17. A method as claimed in any one of claims 14 to 16 in which a flow of cold gas for evaporated liquefied gas is created through the passage.
18. A method as claimed in any one of the preceding claims, in which the passage is not of uniform cross-section.
19. A method of debonding or deflashing substantially as herein described with reference to the accomDanvin drawing
20. Apparatus arranged to perform the method of deflashing or the method of debonding as claimed in any one of the preceding claims, said apparatus comprising an elongate rotary member defining a downwardly inclined passage having at opposite ends thereof an inlet and an outlet for articles to be deflashed or for pieces of composite material to be debonded, means for rotating the elongate member and means for introducing a coolant into the passage.
21. Debonding or deflashing apparatus substantially as described herein with reference to, and as shown in, Figures 1 and 2, 1 and 3, 1 and 4, 1 and 5 or 1 and 6 of the accompanying drawings.