Gas Entrainment and Foam Dispensing Apparatus

Abstract

A foaming and foam dispensing apparatus 100 comprising a cylinder 112 having a piston 132 slidably disposed therein wherein the piston forms two variable volume chambers 134, 136 either side of the pi

Description

Technical Field [0001 ] The present application is concerned with the controlled entrainment of a gas within a single-part compound to generate a homogeneous bubble structure ("foamed material"). More specifically, the present invention is concerned with the forming and dispensing of the generated foam material at a predetermined rate and frequency to form a seal or bond. Background Art

[0002] Dispensed closed cell foams are used in many applications, typically to form seals or to adhere components together. The foam is created from a liquid phase polymer material (typically a thermoplastic) which is heated to a liquid state, and into which a gas is introduced and mixed to create a foam. The mixed foam can then be deposited onto a component under pressure via a nozzle, where it solidifies to form a solid, yet compressible, bead of sealing material.

[0003] EP 0 286 015 A2 discloses a method and apparatus for forming a high viscosity polymer material. Mixing of a liquid polymer and gas occurs in a low energy disk mixer, resulting in a closed cell foam material.

[0004] EP 0 776 745 B1 discloses a method and apparatus for forming a viscous material. A liquid state viscous polymeric material (a thermoplastic polymer) and a gas such as N2, CO2, or air mixed at a low pressure. The mixture is then pressurised by a pump and passed through a tubular conduit. Shear stress created as the mixture passes through the pump, which acts to distribute the gas in the material. The mixture is fed through a nozzle to deposit a bead of material.

[0005] Some examples in the prior art mix and pressurise material with a piston pump. Gas and liquid are fed into a cylinder and pressurised by a piston.

[0006] EP 0 974 391 A1 discloses a system in which two such piston pumps are alternately operated to provide a near-continuous flow of material. This is necessary as each pump needs to be filled before it can be discharged- therefore there is a natural refilling time during which the pump cannot discharge material to the mixer. Using two alternately operated cylinders mitigates this problem.

[0007] US 201 9 / 0337189 discloses a device for forming a viscous material in which a high-pressure gas is injected into a flow of viscous material upstream of a mixing chamber. Once mixed, the foamed material is stored in a conveyor pump for dispensing.

[0008] In some systems, piston pumps are provided downstream of a mixer to store and selectively release foamed material.

[0009] It is an aim of the present invention to provide an improved foaming and dosing apparatus. Summary of Invention [001 0] According to a first aspect of the present invention there is provided a foaming and foam dispensing apparatus comprising: a cylinder having a piston slidably disposed therein, the piston forming two variable volume chambers either side of the piston; a viscous material supply and a gas supply, the viscous material supply and gas supply in communication with a first chamber of the two variable volume chambers; a mixer having a mixer inlet and a mixer outlet, the mixer inlet in fluid communication with the first chamber, and the mixer outlet in fluid communication with a second chamber of the two variable volume chambers, the mixer configured to create a foamed material; a foamed material outlet in fluid communication with the second chamber. [0011 ] Advantageously the present invention utilises both sides of a double acting cylinder and piston arrangementto effect both mixing and foamed material storage and dispensing, making a highly compact and efficient apparatus. The present invention offers efficiency improvements relating to both foam chamber design and energy required within the process, as there is balanced pressure on either side of the piston.

[0012] The mixer is configured to create a homogeneous cell structure of the foamed material. In other words, it increases the level of homogenisation from input (large, inhomogeneous regions of material and gas) to output (smaller, consistently-sized, evenly distributed cells or bubbles).

[0013] Preferably there is a viscous material supply line with an outlet in communication with the first chamber, and a gas supply line with an outlet in communication with the first chamber.

[0014] Preferably there is: a viscous material line valve in the viscous material supply line; and, a gas line valve in the gas supply line a controller configured to control the viscous material line valve and the gas line valve, and to selectively open and closed the viscous material line valve and the gas line valve to provide a predetermined mixture of gas and viscous material in the first chamber. [001 5] Preferably the controller is configured to control the viscous material line valve and the gas line valve dependent on the position of the piston in the cylinder. [001 6] Preferably there is provided: a mixer inlet valve; and, a mixer outlet valve; the mixer inlet valve and the mixer outlet valve controlled by the controller. [001 7] Preferably there is provided: a foamed material outlet valve controlling flow from the foamed material outlet; the foamed material outlet valve controlled by the controller. [001 8] Preferably the foamed material outlet is in fluid communication with a dispensing nozzle. [001 9] Preferably there is provided: a further cylinder having a further piston slidably disposed therein, the further piston forming two further variable volume chambers either side of the further piston; a further viscous material supply and a further gas supply, the further viscous material supply and further gas supply in communication with a further first chamber of the two further variable volume chambers; wherein the mixer is in fluid communication with the further first chamber and a further second chamber of the further two variable volume chambers.

[0020] The mixer inlet may be connected to the further first chamber, or alternatively a further mixer inlet may be provided. The mixer outlet may be connected to the further second chamber, or alternatively a further mixer outlet may be provided.

[0021] Preferably the piston and the further piston are configured to move in alternate stroke directions at any one time, such that as the first chamber decreases in volume, the further first chamber increases in volume.

[0022] The gas supply may be maintained at a pressure in the order of hundreds of kPa, preferably between 300 - 500 kPa, more preferably about 400kPa.

[0023] The material supply may be maintained at a pressure in the order of MPa, preferably between 8 - 12 MPa, more preferably about 10MPa.

[0024] Preferably the system is maintained, between the first chamber of the two variable volume chambers and the foamed material outlet, at a pressure in the order of MPa, preferably between 8 - 12 MPa, more preferably at least 10MPa.

[0025] According to a second aspect there is provided a method of foaming and foam dispensing comprising the steps of: providing: a cylinder having a piston slidably disposed therein, the piston forming two variable volume chambers either side of the piston; and, a mixer having an inlet in communication with a first chamber of the two variable volume chambers and an outlet in communication a second chamber of the two variable volume chambers; in an entrainment stroke moving the piston to: increase the volume of the first chamber, introducing viscous material and gas into the first chamber; and, decrease the volume of the second chamber to expel foamed material from the second chamber; in a mixing stroke moving the piston to: decrease the volume of the first chamber to expel viscous material and gas into the mixer; and, increase the volume of the second chamber to receive foamed material from the mixer.

[0026] Preferably the method comprises the steps of: alternately introducing viscous material and gas into the first chamber in the entrainment stroke.

[0027] Preferably the method comprises the steps of: alternately introducing viscous material and gas into the first chamber dependent on the position of the piston in the cylinder.

[0028] Preferably the method comprises the steps of: providing a further cylinder having a further piston slidably disposed therein, the further piston forming two further variable volume chambers either side of the piston; in an entrainment stroke moving the further piston to: increase the volume of the further first chamber, introducing viscous material and gas into the further first chamber; and, decrease the volume of the further second chamber to expel foamed material from the further second chamber; in a mixing stroke moving the further piston to: decrease the volume of the further first chamber to expel viscous material and gas into the mixer; and, increase the volume of the further second chamber to receive foamed material from the mixer.

[0029] Preferably the entrainment stroke of the piston occurs simultaneously with the mixing stroke of the further piston, and the mixing stroke of the piston occurs simultaneously with the entrainment stroke of the further piston to provide a continuous flow of foamed material to a common outlet. On completion of the material and gas entrainment stroke of the cylinder, its subsequent and uninterrupted mixing stroke through the mixer to refill the dispensing chamber must be completed within the time required for the further piston to entirely dispense. Brief Description of Drawings

[0030] An embodiment of the present invention will now be described with reference to the following figure in which: FIGURE 1 is a schematic view of a first mixing and dosing apparatus in accordance with the present invention; FIGURE 2 is a schematic view of a controller for the apparatus of Figure 1; FIGURES 3a and 3b are schematic views of the apparatus of Figure 1 in different states of operation; and, FIGURE 4 is a schematic view of a second mixing and dosing apparatus in accordance with the present invention. Description of the first embodiment [0031 ] Referring to Figure 1 an apparatus 100 according to the present invention is shown. Configuration

[0032] The apparatus 1 00 comprises a cylinder assembly 102, an air source 1 04, a viscous material source 106, a mixer 1 08 and an applicator 11 0.

[0033] The cylinder assembly 1 02 comprises a cylinder 112 having a main axis A and an outer wall 114 (in this embodiment circular in cross section) defining a cylinder chamber 11 6. The cylinder 112 has a first end 11 8 and a second end 120. Proximate the first end 11 8 there is provided a gas inlet port 122, a liquid inlet port 124 and a first material outlet port 126. Proximate the second end 120 there is provided a mixed material inlet port 128 and a mixed material outlet port 130.

[0034] The cylinder assembly 1 02 is provided with a piston 132. The piston 132 is slidably disposed within the chamber 116 separating it into a first chamber 134 and a second chamber 136. The piston 132 is connected to a piston rod 138 which in turn is connected to an actuator 140 configured to urge the piston along the main axis A of the cylinder 112.

[0035] The air source 1 04 comprises a compressed air tank 142 connected to the gas inlet port 122 with a gas line 144. The gas line has a valve 146 therein. The incoming air pressure is controlled at a constant 4 bar (400kPa).

[0036] The viscous material source 1 06 comprises a pressurised viscous material tank 148 connected to the inlet port 124 with a material line 1 50. The line has a valve 1 52 therein. The incoming material is fed in at between 1 00 and 120 bar (1 0 - 12MPa).

[0037] The mixer 1 08 has an inlet 154 and an outlet 1 56. The inlet 154 is connected to the cylinder first material outlet port 126 via a mixer inlet line 158 with a first mixer valve 1 60. The outlet 156 is connected to the cylinder mixed material inlet port 128 via a mixer outlet line 162 with a second mixer valve 164.

[0038] The applicator 110 comprises a nozzle 166 connected to the mixed material outlet port 130 via an applicator line 168 with a valve 170. The nozzle is configured for material deposition onto a surface 1 0.

[0039] Referring to Figure 2, each of the valves 146, 150, 160, 164, 1 70 are connected to a controller 1 72. The controller 1 72 is configured to actuate the valves and the actuator 140 according to the description below. Use

[0040] A sequence of operation of the apparatus 100 according to the present invention is shown in Figures 3a to 3b. The valve symbols used therein are shown as open and closed according to convention. [0041 ] The apparatus has several strokes, described below: Entrainment stroke

[0042] In Figure 3a, the second chamber 136 is filled with a mixed foam 1 76 (provided in a manner to be described below). The valve 170 is open, meaning that movement of the piston 132 towards the second end 120 of the cylinder (direction D1) by the actuator 140 urges foam from the nozzle 1 66 onto the surface 1 0. Valves 1 60, 164 are closed. Flow from the nozzle occurs at a pressure of 1 00 bar (1 OMPa).

[0043] As the piston starts the entrainment stroke the air valve 146 is open. Material valve 1 52 is closed. At a predetermined linear position of piston 132 the air inlet valve closes and material inlet valve opens (this part of the stroke is shown, but it will be understood that earlier in the stroke 146 was open and 152 closed). The point at which the valves switch from air to material entrainment is determined by a predetermined displacement of the piston 132. Moving this predetermined linear position in the controller settings reduces or increases the degree of air to be entrained in the material. As depicted in Figure 3a this creates an un-foamed unmixed material 178 comprising a gaseous region 178a and a viscous material region 178b. A higher proportion of gas provides a softer, more pliable foam (as is known in the art). The piston displacement in direction D1 can be determined from the actuator 140 (or via a separate position transducer). Mixing stroke

[0044] Figure 3b shows the piston 132 at the end of the entrainment stroke. Practically all mixed, foamed material 176 has been used from the second chamber 136, and the first chamber 134 is filled with unmixed, compressed gas and viscous material 176. The controller commands the actuator 140 to return the piston in direction D2 (opposite to D1).

[0045] Valves 160, 164 are opened (all other valves are closed), meaning that unmixed material from the first chamber 178 is forced through the mixer 108 which mixes it to produce the mixed foamed material 176. This material fills the second chamber as the piston moves back to the first end of the cylinder.

[0046] It will be noted that material is extant in the lines 158, 162 and mixer 1 08 between strokes. Once the piston has returned to the position of Figure 3a (the start of the entrainment stroke), entrainment (and dosing / deposition) can start again.

[0047] It will also be noted that the pressure throughout the system, from the entrainment point (where material is introduced to the cylinder) to exit at the nozzle is kept at a level above 1 00 bar (1 OMPa). This is required to maintain the compressed bubble structure in the viscous material. Description of the second embodiment

[0048] Figure 4 shows a second embodiment of an apparatus 400 according to the present invention. The apparatus 400 comprises two apparatuses 1 00- the first (200) labelled with common features 100 greater (202 etc) and the second (300) labelled with common features 200 greater (302 etc). Both subassemblies 200, 300 are connected to a common mixer 408 with inlet 454 and outlet 256 and a common nozzle 402. It will be noted that the controller(s) are not shown, but are still present in this embodiment.

[0049] In this way, continuous dispensing of the foamed material can be achieved, using a single mixer. The following states are used to provide constant dispensing: State A (depicted in Fig. 4) B Apparatus 200 300 200 300 Stroke Entrainment Mixing Mixing Entrainment Gas valve state 246 Closed 346 Open (part of stroke) 246 Open (part of stroke) 346 Closed Material valve 252 Closed 352 Open (part of stroke) 252 Open (part of stroke) 352 Closed First mixer valve 260 Open 360 Closed 260 Closed 360 Open Second mixer valve 264 Open 364 Closed 264 Closed 364 Open Outlet valve 270 Closed 370 Open 270 Open 370 Closed

[0050] It will be noted that all components (apart from the mixer 408 and nozzle 402) are duplicated for simplicity, but common features can be used / shared, for example: • air source; • viscous material source; • controller; • actuator (in which case the cylinders may be oppositely oriented such that when both pistons are moved in the same global direction, the assemblies carry out different strokes). Variations [0051 ] Specific materials (air and polymeric viscous liquids) have been described as above, but other materials can be used with the present invention. For example, the foam may be made with N2 or CO2, for example.

[0052] Although the fluid sources have been described with tanks containing fluids under pressure, it will be noted that fluids may not be stored in this way and may be provided under pressure in an ad-hoc manner such as with a pump or other form of compressor.

[0053] The orientation of the embodiments shown is purely exemplary, and it will be noted that cylinders according to the invention may be oriented as required by the application and e.g. packaging needs.

[0054] The embodiment of Figure 4 has a shared mixer and a shared nozzle, but equally may have separate mixers and / or separate nozzles.

[0055] The mixers used in the present invention may be any suitable type, including but not limited to: • Simple shear mixing arrangements (i.e. conduits only); • Stirring type mixers having an actuated element; • Tortuous route mixers; • Openings / orifices in plates.

Claims

1. A foaming and foam dispensing apparatus comprising:a cylinder having a piston slidably disposed therein, the piston forming two variable volume chambers either side of the piston;a viscous material supply and a gas supply, the viscous material supply and gas supply in communication with a first chamber of the two variable volume chambers;a mixer having a mixer inlet and a mixer outlet, the mixer inlet in fluid communication with the first chamber, and the mixer outlet in fluid communication with a second chamber of the two variable volume chambers, the mixer configured to create a foamed material;a foamed material outlet in fluid communication with the second chamber.

2. An apparatus according to claim 1, having a viscous material supply line with an outlet in communication with the first chamber, and a gas supply line with an outlet in communication with the first chamber.

3. An apparatus according to claim 2, comprising:a viscous material line valve in the viscous material supply line; and,a gas line valve in the gas supply linea controller configured to control the viscous material line valve and the gas line valve, and to selectively open and closed the viscous material line valve and the gas line valve to provide a predetermined mixture of gas and viscous material during filling of the first chamber.

4. An apparatus according to claim 3, wherein the controller is configured to provide the predetermined mixture by a sequence consisting of the following steps:first, open the gas line valve with the viscous material line valve closed; and,second, open the viscous material line valve with the gas line valve closed;during filling of the first chamber.

5. An apparatus according to claim 3 or 4, wherein the controller is configured to control the viscous material line valve and the gas line valve dependent on the position of the piston in the cylinder.

6. An apparatus according to any of claims 3 to 5, comprising:a mixer inlet valve; and,a mixer outlet valve;the mixer inlet valve and the mixer outlet valve controlled by the controller.

7. An apparatus according to any of claims 3 to 6, comprising:a foamed material outlet valve controlling flow from the foamed material outlet;the foamed material outlet valve controlled by the controller.

8. An apparatus according to any preceding claim, wherein the foamed material outlet is in fluid communication with a dispensing nozzle.

9. An apparatus according to any preceding claim, comprising:a further cylinder having a further piston slidably disposed therein, the further piston forming two further variable volume chambers either side of the further piston;a further viscous material supply and a further gas supply, the further viscous material supply and further gas supply in communication with a further first chamber of the two further variable volume chambers;wherein the mixer is in fluid communication with the further first chamber and a further second chamber of the further two variable volume chambers.

10. An apparatus according to claim 9, wherein the foamed material outlet is in fluid communication with the second further chamber.

11. An apparatus according to claim 9 or 1 0, wherein the piston and the further piston are configured to move in alternate stroke directions at any one time, such that as the first chamber decreases in volume, the further first chamber increases in volume.

12. A method of foaming and foam dispensing comprising the steps of:providing:a cylinder having a piston slidably disposed therein, the piston forming two variable volume chambers either side of the piston; and,a mixer having an inlet in communication with a first chamber of the two variable volume chambers and an outlet in communication a second chamber of the two variable volume chambers;in an entrainment stroke moving the piston to:increase the volume of the first chamber, introducing viscous material and gas into the first chamber; and,decrease the volume of the second chamber to expel foamed material from the second chamber;in a mixing stroke moving the piston to:decrease the volume of the first chamber to expel viscous material and gas into the mixer; and,increase the volume ofthe second chamberto receive foamed material from the mixer.

13. A method according to claim 12, comprising the steps of:alternately introducing viscous material and gas into the first chamber in the entrainment stroke.

14. A method according to claim 13, comprising the steps of:alternately introducing viscous material and gas into the first chamber dependent on the position ofthe piston in the cylinder.1 5. A method according to any of claims 12 to 14 comprising the steps of:providing:a further cylinder having a further piston slidably disposed therein, the further piston forming two further variable volume chambers either side of the piston;in an entrainment stroke moving the further piston to:increase the volume ofthe further first chamber, introducing viscous material and gas into the further first chamber; and,decrease the volume of the further second chamber to expel foamed material from the further second chamber;in a mixing stroke moving the further piston to:decrease the volume of the further first chamber to expel viscous material and gas into the mixer; and,increase the volume of the further second chamber to receive foamed material from the mixer.

16. A method according to claim 15, wherein the entrainment stroke of the piston occurs simultaneously with the mixing stroke of the further piston, and the mixing stroke of the piston occurs simultaneously with the entrainment stroke of the further piston to provide a continuous flow of foamed material to a common outlet.15

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