EP0830904A2

EP0830904A2 - Paint system pressure device

Info

Publication number: EP0830904A2
Application number: EP97306838A
Authority: EP
Inventors: Nicholas Bowman
Original assignee: Black and Decker Inc
Current assignee: Black and Decker Inc
Priority date: 1996-09-07
Filing date: 1997-09-02
Publication date: 1998-03-25
Also published as: GB9618712D0; GB2309265A; EP0830904A3; GB2309265B

Abstract

A paint system comprises a flexible bag (24) for paint, the bag having a sealable opening and a machine (10), adapted to receive the bag of paint. A tube (60) for releasable connection to said opening, and means (70) to connect a paint applicator (80) at the other end of said tube, adapted to receive paint from said bag, through the tube, when the bag is squeezed by the machine. The machine is an open container (12) to receive the bag of paint and has a top edge (9) closed by a lid (14). The edge is provided with a recess (35) adapted to receive a connector (50) for the tube.

A bellows (22) is in the container, a pump (28) being adapted to pressurise the bellows with fluid so as to squeeze the bag, and the bellows having a low friction surface to slide over the bag during inflation and having internal springs to assist deflation of the bag.

The container is specially shaped to remove dead volumes within the container so that the bag can be pressurised to pressures greater than normally accommodatable by the bag.

Description

This invention relates to a paint system of the type broadly disclosed in GB 2142386. In such a system, paint may be supplied to customers in flexible paint reservoirs, or bags. A machine is supplied which contains a bellows, or other pressurising means, arranged to squeeze the bag of paint and force the paint to exit the bag through a tube to a paint dispensing element, such as a brush or roller. The present invention is particularly concerned with a a paint system having a pressure device, in the form of bellows.

In any paint system, it is desirable that the paint rolls well and does not spatter, and this is largely a function of the paint. The best compositions in this regard have a high viscosity when compared with water, for example, but this has the disadvantage that flow of paint along the tube is restricted. Thus to gain sufficient flow of paint to the roller, in order to achieve a reasonable rate of surface coverage, either the diameter of the tube should be large, or the pressure developed by the machine must be large.

The former requirement has the disadvantage that, with a large diameter tube, a large volume of paint remains unusable in the tube when the paint bag is empty and pressure in the system drops. The latter requirement is therefore preferred, and this calls for strength in the design of the machine.

While a pressure vessel adapted to be pressurised with air and containing a bag of paint is feasible, there are inherent disadvantages with such a design. Firstly, an opening must be provided, giving user access to the bag of paint inside the container and seal arrangements must be provided around the opening. Such seal arrangements must be capable of continual interruption when each bag of paint is replaced after depletion. Secondly, an effective seal must be provided around the tube exiting the container. Hence a bellows arrangement is preferred because none of such sealing arrangements are required.

However, there is a limit to the pressure which can be developed by the bellows, because it exerts a localised force on the bag. The strength of the bag determines the maximum pressure, and if the bellows creates a pressure greater than can be withstood by the bag, there is the danger that the bag will explode. Thus a compromise has to be reached.

It is an object of the present invention to provide a paint system which not only meets this compromise but exceeds it.

In accordance with a first aspect of this invention there is provided a paint system comprising:-

a) a flexible plastics material bag for paint, the bag having a sealable opening;

b) a machine adapted to receive the bag of paint;

c) a tube for releasable connection to said opening;

d) means to connect a paint applicator at the other end of said tube, which applicator is adapted to receive paint from said bag, through said tube; wherein the machine comprises:-

e) an open container shaped to receive snugly within its confines the bag of paint;

f) a lid to close the container;

g) a bellows in the container to squeeze the bag of paint against the sides of the container;

h) a pump adapted to pressurise the bellows with fluid so as to effect said squeezing of the bag;

wherein the bellows comprises an envelope of flexible material whose surface has a low coefficient of friction with respect to the plastics material of the bag.

In such an arrangement, the bellows slides over the bag as it inflates and does not impose such localised pressure forces on the bag. More especially, it does not grip the bag against opposite side walls of the container, so that chords of the side walls of the bag across the container are not experienced. Such chords prevent reduction of bag volume on further pressurisation of the bellows.

Preferably, the bag comprises an envelope of two substantially rectangular sides welded along their edges, the opening being formed in a top corner thereof and a gusset being formed along a bottom thereof, whereby, when filled with paint, the bag has a substantially circular cylindrical form with a gusset region forming a rectangular chamfered base of the bag and with a flattened, tapering top region, and wherein the container has itself a rectangular chamfered base on which said gusset region is adapted to lie.

Preferably, the container has an open top forming a substantially circular cylindrical opening and having a flattened side against which said bellows are positioned, an internal wedge being formed in said container around said top opposite said flattened side and adapted to support said top region of the bag.

Preferably the tube includes a connector for said connection to the opening of the bag, wherein the connector is adapted to be captured in a recess formed in the top of the container. Such capturing holds the bag in the correct position in the container, particularly when it is not full, so that complete emptying of the bag on pressurisation of the bellows can be ensured.

With such an arrangement, it is possible to have a narrow tube and yet achieve the requisite flow of paint along it because the pressure developed by the bellows can be permitted to exceed the maximum pressure capable of being withstood by the bag. This is possible because the container is specially shaped to support the bag over the surface thereof not pressed by the bellows, and the bellows has a low friction surface so that as it expands it slides over the bag minimising localised forces on the bag.

Preferably the bellows comprises an envelope having two sides, and two gussets between the sides along opposite edges of the sides. The gussets are preferably interconnected inside the bellows by elastic elements serving to pull the gussets together to assist deflation of the bellows.

Preferably the sides of the bellows are constructed from a laminate of elastomeric sheet to which is fixed woven fabric sheet. Preferably the woven fabric is cotton. In this event, the material of the bellows is flexible, but not elastic.

Although the word "paint" is used exclusively herein, it should be understood to include any liquid, and, indeed, while the invention is described exclusively in relation to the application of paint, which in this context includes other surface coating compositions such as varnishes, stains and lacquers, the concepts embodied in the present invention may be employed in the dispensing of liquids completely unrelated to surface coating compositions.

The invention is further described hereinafter with reference to the accompanying drawings, in which:-

Figure 1 is a perspective view of a paint system machine according to the present invention;

Figure 2 is a view similar to Figure 1, but with the handle of the machine in its open position;

Figure 3 is a side view of a full paint bag connected to a tube and paint applicator;

Figure 4 is a side section through the paint system machine of Figures 1 and 2, with the addition of a deflated bellows and a pump unit according to the present invention;

Figure 5 is a side view of an empty paint bag in accordance with the present invention;

Figures 6 a to e are different views of a paint bag showing its general shape when full, except Figure 6c which is empty, where 6a is a section on the line A-A in 6e, 6b is a front view, 6c is a back view (when empty), 6d is a bottom view, and 6e is a side view;

Figure 7 is a front view of the bellows in Figure 4;

Figures 8a to c show different panels of the bellows of Figure 7, 8a showing a top gusset, 8b a back panel, and 8c a bottom gusset, the front panel being visible in Figure 7, and Figure 8d being a section through the bellows, similar to it shown in Figure 4;

Figures 9 a, b and c are top views of the paint machine in its open condition in three stages of depletion of a paint bag therein;

Figures 10 a, b, c and d are side views/side sections of a paint bag opening element, cap, and connector, Figure 10a showing the opening with cap fitted, 10b showing opening with cap removed and connector adjacent, 10c opening with connector connected, and 10d a section on the line D-D in Figure 10a;

Figure 11 is an end view of the connector of Figure 10;

Figures 12 a and b are sections on the lines A-A and B-B in Figures 10b and 10c respectively;

Figure 13 is a side section through the top part of the paint machine; and

Figures 14 a to d are a rear view, top plan view, side view and front view of a base insert for the paint machine.

In Figure 1 is shown a paint application machine 10 which comprises a hollow container 12, a back cover 18 and a closing handle 16. The container includes a bellows (22, Figure 4) pressurised with fluid by a pump unit (28, also Figure 4). The back cover 18 is shown in Figure 1, but is removed from Figure 2. In Figure 2, the handle 16 is in its open position, when a lid 14 is openable.

Referring to Figures 3 and 4, container 12 has an internal space 20, a back side wall 13, and a base 15. Back cover 18 defines with the container 12 two spaces, one on each side of the machine and only one of which, 90 is visible in the drawings. In this space 90 is disposed the pump unit 28. In the other space is disposed a battery to power the pump unit. A tube 26 exits the pump unit and is connected to connector 198 at the bottom of bellows 22. Bellows 22 comprises two sheets or panels 190,192 of cotton covered, elastomeric material, connected by like material top and bottom gussets 194,196 respectively. Lid 14 is pivoted about axis 32 to container 12 and a flap 27 of the bellows is connected to the lid. Connector 50 extends from container 12 through a recess 34 in top edge 9. A second flap 25 of the bellows is connected to back wall 13 of the container 12.

The pump unit 28 is operated by a button 30 and is powered by the battery (not shown). The paint bag 24, when filled with paint, is placed in the container 12 where it nestles close to the bellows 22, and fits snugly inside the volume 20. When the button 30 is depressed, the pump unit 28 pressurises bellows 22 which expand and compress the paint bag 24. Paint in the bag is then squeezed out through an opening 40 of the bag, through a connector 50 on the end of a tube 60, along the tube and thence to a handle 70 and an applicator 80. A control knob 72 on handle 70 is used to control flow of paint to roller arrangement 80 so that sufficient paint is supplied to maintain the requisite wetness of the roller as it is rolled over a wall or other surface to which paint is to be applied.

The container top edge and lid have

respective recesses

34,36 adapted to receive and capture the connector 50 when correctly oriented as explained further below. When the lid is closed, handle 16 can be pivoted to the position shown in Figure 1 where it prevents the lid from opening.

As mentioned above, it is desirable to have a high pressure system so that paint flows even along a relatively narrow tube 60. Thus container 12 has substantial latticing on its flat surfaces, that is to say along its back surface 13 and bottom 15, in order to provide reinforcement of those surfaces. Curved surfaces of the container do not require such reinforcement. The lid 12 is likewise latticed. With this arrangement pressures of the order of 1.5 bar above atmospheric can be accommodated, although only about 1 bar above atmospheric is found to be necessary to provide the requisite flow rate.

With such high pressures, it is necessary that the paint bag be sufficiently strong, but such bags are expensive. Thus the present invention provides an arrangement where the strength of the bag is not entirely limiting on the pressure appliable.

Figure 5 shows a paint bag 24, which comprises a plastics envelope welded around its periphery 110. A carrying handle 120 is formed in one corner, and in the other is the opening 40. The opening 40 comprises a discrete opening element 41 captured by the bag envelope and welded to it. Element 41 comprises a weld part, or base, 122 having tapering lead-in, lead-out regions 124,126 enabling reliable welding to the bag envelope. Behind the weld part is connected a dip element 128 which serves to keep the walls of the envelope apart and ensure a passage for paint in the bag from the bottom of the bag to the opening. A passage 130 is formed through the weld part and into a neck 132 of the element 41. The dip element 128 is essentially cruciform in section and connects with the weld part at four points 134 providing access to the bag interior from the passage 130.

Figure 6 shows the bag construction in more detail. Between two sides 112a and b of the bag is a bottom gusset 114 which is rectangular in shape. When the bag is empty, the gusset is folded in half along its length along fold line 114a and its ends 114b are welded together and between sides 112a,b at 114b. Moreover, the sides 112a,b are each separately welded to the gusset 114 along two base edges 110c and two triangulating fillets 116a,b at each end of the gusset 114.

Thus the essential shape of the bag when it is full is circular cylindrical, with gusset region having a squared base from which four chamfers lead to the cylindrical part, and a flattened, tapering top region extending from the cylindrical part.

Figures 7 and 8 show the bellows 22, which is a double envelope comprising front and back sheets 190,192 of flexible, gas impermeable material, preferably an elastomer sheet having a woven cotton layer attached to aid slippage against the plastics material of the bag 24. Upper and lower gussets 194,196 are provided between the sheets 190,192, each folded in half along respective lines 194a,196a when the bellows is deflated and flat. The bellows is substantially octagonal in profile which corresponds to the side profile of the bag 24.

Between lower gusset 196 and back sheet 192, an opening 198 is formed for connection of air tube 26. Flap 27 is an extension of front sheet 190, while flap 25 is an extension of gusset 194. The gussets 194,196 are connected internally of the bellows by elastic elements 200. These serve to assist deflation of the bellows when air pressure is released. This occurs when button 30 is disengaged both switching off pump unit 28 and opening a dump valve (not shown) provided in a pressure chamber of the pump unit. The elastic elements pull the gussets towards their fold lines 194a,196a. Moreover, opening of the lid 14 further assists deflation, because flap 27 is bent back, as can be seen in Figure 4, and, since the bottom of the bellows is connected, by means not shown, to the bottom of the back wall 13 around the opening 198, the bellows is further urged into its collapsed condition.

Referring now to Figure 10, neck 132 of the opening element 41 of the bag 24, has, from its connection to the weld part 122, a flange 136, a screw threaded region 138, a bayonet region 140, and a mouth 142 for the passage 130. Flange 136 has four equi-spaced detents, or notches, 144. A cap 145 is internally screw threaded for engagement with screw thread 138 on the neck 132 of the opening. Bayonet 140 of the neck 132 comprises merely a quarter to one third turn screw thread 141, one on either side of the neck.

Connector 50 comprises two discrete elements, a main connector body 150 and a connection element 152. Connector body 150 has a connection region 154, a flexible region 156, a support region 158 and a protection region 160. The tube 60 passes through the connector body and is press fitted over one end 162 of connection element 152. A circumferential rib 164 aids sealing and also ensures a tight fit when the connector body 150, is slid over the tube and snapped into engagement with the element 152, barbs 166 on the element snapping into windows 168 in the body 150. A sleeve 170 of the body closely surrounds the end 162 of the element 152 and presses the tube into engagement with the rib 164 securing the connection of the tube to the element 152.

Behind the connection region of the connector 150 is the flexible region 156. The reason for this region is explained further below, but it comprises an helical formation 172 which gives the region flexibility but at the same time a certain amount of rotational rigidity about the long axis of the connector, at least in the direction of tightening of the helix 172. While the flexible region provides flexibility, nevertheless it still has radial rigidity and prevents the tube 60 from being compressed by the bellows as it inflates. If such compression were to occur, the tube might be closed preventing exit of the paint along the tube.

Beyond the flexible region is the support region 158 which, in Figures 10b and 10c is shown in two alternative forms, cross sections of each form being shown in Figures 12a and 12b respectively. The Figure 10b embodiment is preferred and, apart from comprising a rigid sleeve 174 which both embodiments employ, it has two depending pillars 176 either of which is adapted to be received in an eye 35 formed in the base of recess 34 of the container 12. In Figures 10c and 12b, the support region is given a rectangular section adapted to be received in the recess 34, which recess would be correspondingly shaped and so as to ensure only two possible orientations of the connector in the recess.

Finally the protection region 160 extends from the support region 174 and may, like the flexible region comprise a helix, or as shown may comprise a lattice type arrangement. In either case, it is provided merely to ensure that the tube exiting the support region cannot kink through a small angle but is supported over a larger radius of bend by the protection region 160. The flexible region 156 may also be arranged as a lattice formation, but a helix is preferred for both given its greater flexibility.

The passage 130, over a distance at least as long as its diameter, has a smooth circular cross-section from its mouth 142. Likewise, connection element 152 has a smooth external circular cross-section 153 over a similar length from its own mouth 178. Near its mouth, the connection element 152 has a circumferential groove in which is disposed an elastomeric O-ring 155, adapted to provide a seal against passage 130 when the connector 150 is engaged with bag opening 40.

About the connection element 152, the connector body 150 in its connection region 154 has a pair of bayonet dogs 180 (see also Figure 11). These are adapted to be engaged in entries 143 of bayonet screw thread 141 of neck 132. When dogs 180 are engaged with thread 141 and the connector is turned through about 90 degrees, two lugs 182 engage flange 136 on neck 132 of the bag opening 40. When the connector is turned fully, the lugs snap into detent notches 144 in the flange 136. Visual indication that correct connection has been made is provided by wings 184 of a collar forming connection region 154, which wings 184 correspond in shape, and alignment when the connector 50 is correctly connected, with the tapering lead-in, lead-out regions 124,126 of weld part 122 of the opening element 41.

Turning now to Figure 9, this illustrates the process of bag 24 emptying of paint during use as the bellows 22 expand. The lid 14 is shown open for the sake of clarity, although, in fact, arrangements not fully discussed herein prevent operation of the machine 10 while the lid is open. Indeed, the flap 27 of the bellows appears to grow in Figures 9a, b and c, but of course this is not, in reality, the case, although the flap does move during bellows inflation under its connection to the lid when the lid is closed.

When the bag 24 is full and received within volume 20 of the container 12, it occupies most of that volume conforming itself to the shape of the container. The bellows 22 is completely deflated and lies flat against back wall 13 of the container 12. When the connector 50 is correctly connected to bag opening 40, not only is this visually apparent by close alignment of wings 184 and weld element 122, but also support region 158 fits quickly and easily into recess 34 of the container with pillar 176 entering eye 35 therein. There may be slight bending necessary of the flexible region 156. With the connector 50 in place in the recess 34, the lid is closed and so makes a connection between the bag and container to hold the bag in correct position in the container. This is more important when a half empty bag is inserted which does not have as much inherent shape as a full bag which naturally tends to adopt the correct position. Even so, the position of the connector on the bag, and fitting the connector in the recess, ensures the correct rotational position (i.e. about a vertical axis of the bag) in the container 12.

When the machine is switched on, the bellows 22 begins to inflate and squeeze the bag 24 in the container 12 so that paint therein exits through bag opening 40, through connector 50 into tube 60, and thence to handle 70 and paint applicator 80 for application to a surface such as a wall. As the bag is emptying as shown in Figures 9b and 9c, the centre line of the bag moves away from back wall 13, so that flexible region 156 of the connector 50 flexes beyond an in-line position as shown in Figure 9b and to a fully bent-back position as shown in Figure 9c when the bag is substantially empty and the connector is pressed against the front wall of the container.

From the foregoing description, it will now be apparent why it is required that the length of the overlapping

circular section parts

130, 153 of the opening and connector respectively is at least as great as the diameter of such parts. This ensures that flexing which takes place in the connector as described above does not result in leakage around the seal.

The bellows adapts itself to the shape of the bag and slides over it as the bag changes shape on gradual opening. This is crucial in ensuring that, as the bag 24 empties, its edges 24a (see Figure 9c) do not trap the bag against the side wall of the container and form a chord (dashed line 24b) across the container which would isolate the region of the bag 24 between the chord and wall so that, no matter what pressure the bellows developed, the volume enclosed would be relieved of pressure and paint contained therein could not be expelled. In any event, if such a chord did develop, the tension in it could be sufficient to tear the bag because of the pressure capable of being developed by the bellows.

Secondly, it is important to remove dead space within the container into which the bag might expand, and possibly burst under the pressures developed. For this reason a base insert 300 (see Figure 14) is received on the bottom wall 15 of container 12, which insert has front flange 302 and side flanges 304. Together with bottom front face 306 of the bellows 22 (see Figure 4), these flanges 302,304 support the chamfered regions 308 (see Figure 6) of the bottom of bag 24. Moreover, referring to Figure 13, a curved wedge element 310 is fixed around the top edge 9 of the container 12 to support the flattened top region of the bag 24.

Claims

A paint system comprising:-

a) a flexible plastics material bag for paint, the bag having a sealable opening;

b) a machine adapted to receive the bag of paint;

c) a tube for releasable connection to said opening;

d) means to connect a paint applicator at the other end of said tube, which applicator is adapted to receive paint from said bag, through said tube; wherein the machine comprises:-

e) an open container shaped to receive snugly within its confines the bag of paint;

f) a lid to close the container;

h) a bellows in the container to squeeze the bag of paint against the sides of the container;

i) a pump adapted to pressurise the bellows with fluid so as to effect said squeezing of the bag; wherein the bellows comprises an envelope of flexible material whose surface has a low coefficient of friction with respect to the plastics material of the bag.
A paint system as claimed in claim 1, wherein the bag comprises an envelope of two substantially rectangular sides welded along their edges, the opening being formed in a top corner thereof and a gusset being formed along a bottom thereof, whereby, when filled with paint, the bag has a substantially circular cylindrical form with a gusset region forming a rectangular chamfered base of the bag and with a flattened, tapering top region, and wherein the container has itself a rectangular chamfered base on which said gusset region is adapted to lie.
A paint system as claimed in claim 2, wherein the container has an open top forming a substantially circular cylindrical opening and having a flattened side against which said bellows are positioned, an internal wedge being formed in said container around said top opposite said flattened side and adapted to support said top region of the bag.
A paint system as claimed in any preceding claim, wherein the tube includes a connector for said connection to the opening of the bag, wherein the connector is adapted to be captured in a recess formed in the top of the container.
A paint system as claimed in claim 4, wherein the connector comprises a support region adapted to be received in said recess, a connection region for connection to said bag, and a flexible region between said connection and support regions, which flexible region permits adjustment of the position of the connection region relative to the support region during emptying of the bag in use of the system.
A paint system as claimed claim 5, wherein the tube is itself flexible and passes through the support region of the connector to the connection region thereof, the connector protecting the tube against compression when the bag is squeezed by the machine.
A paint system as claimed in claim 6, wherein the connector has a protection region beyond the support region with respect to the connection region to support flexibly the tube exiting the support region.
A paint system as claimed in any of claims 5 to 7, wherein the regions of the connector are a single integrated moulded plastics component, the flexible region comprising a helix joining said support and connection regions.
A paint system as claimed in claim 8, wherein the connector comprises a connection element which is discrete with respect to said regions of the connector, and is captivated in said connection region.
A paint system as claimed in claim 9, wherein said connection element has one end connected to the tube and its other end forming a circular-cylindrical section of the connector for sealing engagement with a corresponding section of the opening of the bag.
A paint system as claimed in any preceding claim, wherein the bellows comprises an envelope having two sides, and two gussets between the sides along opposite edges of the sides.
A paint system as claimed in claim 11, wherein the gussets are between top and bottom edges of the two sides.
A paint system as claimed in claim 11 or 12, wherein the gussets are interconnected inside the bellows by elastic elements serving to pull the gussets together to assist deflation of the bellows.
A paint system as claimed in claim 11, 12 or 13, wherein the sides of the bellows are substantially octagonal.
A paint system as claimed in any preceding claim, wherein the sides of the bellows are constructed from a laminate of elastomeric sheet to which is fixed woven fabric sheet.
A paint system as claimed in claim 15, wherein the woven fabric is cotton.