PAINT BRUSH

Abstract

Described is a paint brush that includes: a handle; a ferrule secured to the handle; and a brush head including a plurality of synthetic bristle filaments extending in a longitudinal direction from the ferrule. The brush head has a width dimension and a thickness dimension in a plane perpendicular to the longitudinal direction, with the width dimension being greater than the thickness dimension. Each filament has a fixed end secured at the ferrule and an opposite free end longitudinally distant from the ferrule. The free ends of at least a portion of the filaments collectively define a substantially chisel-shaped tip profile in a plane perpendicular to the width dimension such that an apex of the chisel-shaped tip extends across the width of the brush head. Every filament in the brush head is tapered over at least 60% the filament length.

Claims

1. A paint brush comprising: a handle; a ferrule secured to the handle; and a brush head comprising a plurality of synthetic bristle filaments extending in a longitudinal direction from the ferrule, the brush head having a width dimension and a thickness dimension in a plane perpendicular to the longitudinal direction, with the width dimension being greater than the thickness dimension, and each filament having a fixed end secured at the ferrule and an opposite free end longitudinally distant from the ferrule, wherein the free ends of at least a portion of the filaments collectively define a substantially chisel-shaped tip profile in a plane perpendicular to the width dimension such that an apex of the chisel-shaped tip extends across the width of the brush head.

2. The paint brush of claim 1, wherein the chisel-shaped tip is a symmetrical, rounded V-shaped tip with a rounded apex.

3. The paint brush of claim 2, wherein sides of the V-shaped tip form an internal angle of less than 90 degrees.

4. The paint brush of claim 1, wherein every filament in the brush head is tapered from its fixed end to its free end, with the taper of each filament extending over at least 60% of its length.

5. The paint brush of claim 4, wherein each filament is tapered over at least 75% of its length.

6. The paint brush of claim 4, wherein each filament is substantially linearly tapered.

7. The paint brush of claim 6, wherein the thickness of each filament at its fixed end is substantially the same as the thickness of all other filaments.

8. The paint brush of claim 4, wherein the thickness of each filament at its fixed end is in the range of 0.15 to 0.30 mm.

9. The paint brush of claim 4 wherein the thickness of each filament at its free end is in the range of 0.01 to 0.1 mm.

10. The paint brush of claim 1, wherein the filaments within the brush head vary in length and at least a portion of the filaments have free ends which stop short of the chisel-shaped tip.

11. The paint brush of claim 10, wherein filaments of varying length are distributed throughout the width and thickness of the brush head.

12. The paint brush of claim 11, wherein a length of the shortest filaments is 30% to 60% of a length of the longest filaments, each measured from the ferrule to the filament tips.

13. The paint brush of claim 12, wherein the length of the longest filaments is about 90 mm and the length of the shortest filaments is about 30 to 40 mm, each measured from the ferrule to the filament tips.

14. A paint brush comprising: a handle; a ferrule secured to the handle; and a brush head comprising a plurality of synthetic bristle filaments extending in a longitudinal direction from the ferrule, the brush head having a width dimension and a thickness dimension in a plane perpendicular to the longitudinal direction, with the width dimension being greater than the thickness dimension, and each filament having a fixed end secured at the ferrule and an opposite free end longitudinally distant from the ferrule, wherein every filament in the brush head is tapered from its fixed end to its free end, with the taper of each filament extending over at least 60% of its length.

15. The paint brush of claim 14, wherein each filament is tapered over at least 75% of its length.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows a front view of a paint brush in accordance with an example embodiment of the invention

[0037] FIGS. 2 and 3 show perspective and side views of the brush head and ferrule of the paint brush shown in FIG. 1.

[0038] FIG. 4 is a side cross-sectional view of the paint brush shown in FIGS. 1 to 3 and highlighting certain parameters of the overall profile and tip shape.

[0039] FIG. 5 shows a side view of a tip portion of the paint brush depicted in FIGS. 1 to 3 (left-hand side) alongside a tip portion of a conventional paint brush (right-hand side).

[0040] FIG. 6 shows a partial cutaway perspective view of the brush head and ferrule portions of the paint brush depicted in FIGS. 1 to 3.

[0041] FIG. 7 shows a side view of a single filament of the paint brush shown in FIGS. 1 to 3.

[0042] FIGS. 8A to 8C show perspective, front and side views of another paint brush in accordance with an alternative embodiment of the invention.

[0043] FIGS. 9A to 9C show perspective, front and side views of another paint brush in accordance with a further alternative embodiment of the invention.

[0044] FIGS. 10A to 10C show perspective, front and side views of another paint brush in accordance with a further alternative embodiment of the invention.

[0045] FIGS. 11 and 12 show performance test results for the paint brush shown in FIGS. 1 to 3 compared to a typical prior art paint brush, the tests being carried out using the same painting program/actions of a robotic painting system.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0046] Referring firstly to FIG. 1 of the drawings, there is shown a front view of a paint brush 10 in accordance with an example embodiment of the invention. This paint brush 10 comprises a handle 12, a ferrule 14 secured to the handle 12, and a brush head 16 comprising a plurality of synthetic bristle filaments 18 (best seen in FIG. 6) extending in a longitudinal direction (vertically in FIG. 1) from the ferrule 14.

[0047] It will be appreciated by persons skilled in the art that the drawings show a somewhat idealised shape of the brush head 16, given the dynamic and somewhat undefined nature of thousands of individual flexible bristle filaments 18. However, in general, the drawings show the overall shape of a dry unused paint brush. This shape would of course change somewhat when the brush is wet with paint.

[0048] FIG. 2 shows a perspective view and FIG. 3 shows a side view of brush head 16 and ferrule 14 of the paint brush 10, although in these figures the brush is up the other way with the brush head 16 held upwardly from the ferrule 14.

[0049] The brush head 16 and ferrule 14 have a generally rectangular cross-sectional profile, in a plane perpendicular to the longitudinal direction, with a width W greater than a thickness T. Other cross-sectional profiles are possible and, in general, the width W extending across the front face of the brush 10 as shown in FIG. 1 is greater than the thickness T extending from front to back as shown in the side view of FIG. 3.

[0050] Each filament 18 of the brush head 16 has a fixed end 20 secured at the ferrule 14, thus forming a base of the filament 18, and an opposite free end 22 longitudinal distant from the ferrule 14. In one method of construction, each filament 18 may be held within the ferrule 14 using one or more blocks or wedges (not shown) and an epoxy adhesive, in a conventional manner.

[0051] The free ends 22 of at least a portion of the filaments 18, and more specifically the longest filaments within the brush head 16, collectively define a substantially V-shaped chisel tip 24 of the brush head. As can be best seen in FIGS. 3 and 4, this V-shape lies in a plane perpendicular to the width W of the brush head, across its thickness direction T, to form a rounded apex 26 at a midpoint of the brush head 16. The chisel is thus symmetrical in this instance. It should be appreciated however that the V may be made asymmetrical such that the apex is positioned towards one face or the other of the brush head. As can be seen in FIG. 2, the apex 26 extends across the full width W of the brush head, in this example.

[0052] Referring now to FIG. 4, there is shown a side cross-sectional view of the brush head 16 and ferrule 14 of the brush 10 shown in FIGS. 1-3. The brush head 16 comprises a plurality of synthetic bristle filaments with a fixed end secured to the ferrule 14. Each filament extends upwardly from the ferrule 14 and the longest of the filaments collectively define an inverted V shaped tip profile 24, in a vertical plane extending across the thickness dimension T. The V-shaped tip 24 has a rounded apex 26 and somewhat flat side faces 28 extending from the rounded apex 26 to the front and rear faces of the brush head 16.

[0053] While the apex 26 is shown with a somewhat rounded contour, given the dynamic nature of all the movable individual bristle filaments, the primary V shape of the chisel tip 24 is illustrated by the overlaid inverted V 27 having an internal angle ? which, in this preferred embodiment, is about 60?. It will be appreciated however that a sharper or flatter V shape could instead be employed, according to the particular requirements of a specific brush. This is one of the many factors which can be used to fine tune the characteristics of the brush.

[0054] For comparison purposes, FIG. 5 shows a side view of the tip portion of two paint brushes, with the brush 10 on the left hand side being made in accordance with an example embodiment of the present invention and the brush 50 on the right hand side being a conventional paint brush. As can be seen in this side view of the two brushes, the brush 10 has a V-shaped chisel tip 24 with an apex 26, in contrast to the brush 50 having a rounded end surface 52.

[0055] Referring now to FIG. 6, there is shown a partial cross section of the brush 10 of FIGS. 1-3 with a portion of its filaments 18 being cut away so that a central cross-section across the thickness of the brush head 16 can be seen. It is to be noted that the filaments 18 within the brush head 16 vary in length and a portion of the filaments have free ends which stop short of the V-shaped chisel tip. For example, the filaments labelled 19 stop significantly short of the tip, even though many of them are located within a central region of the brush head 16. In the preferred embodiment, filaments of various lengths are distributed throughout the width and thickness of the brush head 16.

[0056] Referring now to FIG. 7, there is shown a side view of a single filament 118 having a first end 120, which in the finished paint brush is fixed to the ferrule, and a second end 122, which in the finished paint brush is free and thus forms a tip of the filament 118. As can be seen, the filament 118 has a length L and is tapered, with its first end 120 being thickest and its second end 122 being thinnest. Accordingly, if the cross-section of the filament 118 is round, the filament forms a very long and fine cone shape. In some embodiments, the filament 118 is tapered in a linear manner along its entire length L, however achieving this is a challenge given the very small dimensions of the filaments involved, and slight variations inevitably occur in the tapering process.

[0057] The inventors have found that tapering of the filaments is best performed chemically. In this regard, each filament, after being extruded and cut to length, is immersed in a strong alkali solution for a period of time, such that the alkali solution eats away part of the polymer leaving it with one end tapered. Greater tapering is achieved by greater length of the filament being immersed in the solution and for a longer period. Achieving a desired or uniform taper thus requires careful positioning and monitoring of the length of the filament immersed in the solution and the period of immersion.

[0058] The inventors have found that with tapered filaments it is possible to provide an optimum combination of stiffness at the base of the filaments (near the ferrule) and softness at the tips. The greater stiffness at the base provides greater control of the brush head while the softer tips in contact with the surface give an improved surface coverage and smoother finish with minimal brush strokes visible in the surface once the paint is dry. The amount of taper employed for each bristle can be selected, and effectively tailored for a particular type of brush, including type of paint/coating or intended use. Combinations of filaments having greater and lesser tapered filaments can be created for specific purposes.

[0059] In preferred embodiments of the paint brush, every filament within the brush head is tapered. However, all filaments need not all be tapered to the same degree or with the same profile. It is considered that a person skilled in the art would readily be able to conduct the necessary experiments, without undue burden, to optimise the degree and length of taper desired for any specific purpose.

[0060] Compared to conventional paint brushes, the inventors have found that it may be advantageous for the thickness of each filament at its fixed end (i.e. where it meets the ferrule) to be slightly greater than the thickness of conventional synthetic filaments used in the manufacture of prior art paint brushes. For example, in the preferred embodiment, the thickness of each filament at its fixed end is at least around 0.20 mm and preferably around 0.23 mm. In contrast, filaments used in prior art paint brushes are typically less than 0.20 mm.

[0061] The inventors have found that increased thickness, and hence stiffness, of the filaments towards the ferrule gives more structure to the brush head and a stiffer overall feel to the brush. In turn, this gives better control of the filaments' free ends, enabling greater precision when cutting in around edges. At the same time, the fine and soft tips of the filaments enable a painter to more easily apply very light pressure when laying off the wet paint on the surface, thereby delivering a smoother and more even finish with virtually no brush marks. The V-shaped tip profile of the brush head further enhances this effect by reducing the number of filament tips which make final contact with the paint surface.

[0062] Turning now to FIGS. 8A to 8C, there is shown an oval cutter paint brush 60 made in accordance with an alternative embodiment of the invention. In the oval cutter 60, the brush head 62 has an ovular cross-sectional profile (in a horizontal plane in the drawings) but is otherwise similar to the brush 10 show in FIGS. 1-3. Again, the brush 60 has a V-shaped chisel tip 64 having an apex 66 extending across the full width of the brush head 62. However, the oval cross section of the brush head 62 causes the flat sides 68 of the V-shaped chisel tip 64 to become crescent shaped as the surfaces divert away when viewed from the front (see FIG. 8B).

[0063] FIGS. 9A to 9C show an angled oval cutter paint brush 70 made in accordance with another alternative embodiment of the invention. The angled oval cutter 70 is similar to the oval cutter 60 shown in FIGS. 8A to 8C except that the tip is angled, or sloped, across the width of the brush, as best seen in the front view of FIG. 9B. Again, the brush 70 has a V-shaped chisel tip 74 having an apex 76 extending across the full width of the brush head 72. The oval cross section of the brush head 72 again causes the flat sides 78 of the V-shaped chisel tip 74 to become crescent shaped, although slightly lopsided in this instance, when viewed from the front (see FIG. 9B).

[0064] FIGS. 10A to 10C show an angled sash paint brush 80 made in accordance with yet another alternative embodiment of the invention. The angled sash 80 has a substantially rectangular cross-sectional profile (in a horizontal plane in the drawings) but with rounded ends 81. This brush is similar to the brush 10 shown in FIGS. 1-3 except that it has a V-shaped chisel tip 84 angled across the width of the brush head 82, as best seen in the front view of FIG. 10B. In this regard, the angled sash 80 is similar to the angled oval cutter 70 shown in FIGS. 9A to 9C but the flat sides 88 of the V-shaped chisel tip 84 form a somewhat trapezoidal shape rather than a crescent shape. Again, the V-shaped chisel tip 84 has an apex 86 extending across the full width of the brush head 82.

Performance Testing

[0065] The inventors have conducted various tests on a sample paint brush manufactured in accordance with a preferred embodiment of the present invention and compared its performance to more conventional paint brushes. More specifically, the sample brush was tested for its paint application performance using an automatic robot painting test system. This system ensures uniform and repeatable test conditions for each sample brush. A robot arm grasps each brush, loads it with paint and then applies the paint to a surface. The system captures before and after weight measurements and builds up a set of performance data of a predefined painting action. Each test takes place on a wall such that the painted surface is vertical in each test.

[0066] FIGS. 11 and 12 show photographs of two test samples of paint applied to white paper using 63 mm wide paint brushes. In each photograph, the left-hand set of paint stripes was produced by a conventional paint brush and the right-hand set of paint stripes was produced by a paint brush made in accordance with a preferred embodiment of the present invention.

[0067] FIG. 11 shows the result of a single cycle (i.e. a single coat of paint) from the very first use of each paint brush and FIG. 12 shows three cycles (i.e. three coats of paint) with each cycle overlaid and all other criteria being equal for comparison.

[0068] In each instance the robot arm grips the paint brush and, after loading with paint, applies four paint stripes to the paper, using an identical action in each instance, without reloading the brush with paint between stripes. As can be seen from the resulting paint pattern shown in the images, the brush commences at the upper left-hand corner, paints vertically downward to create a first stripe, then lifts and moves horizontally to the right, paints upwardly to create a second stripe, moves horizontally to the right and repeats the action to thereby produce four stripes in total. The same painting sequence is then repeated for the other brush, using an identical painting motion.

[0069] The test results shown in FIG. 12 result from the same sequence of motions as the test shown in FIG. 11 but three coats of paint are overlaid. The two brushes tested are the same as the two brushes used in the test of FIG. 11.

[0070] In each test sequence, the same paint is used (from the same paint pot) and hence the same viscosity. The test sequence is conducted on the same time/day and thus the temperature and humidity are the same. The robot follows a pre-programmed series of broad stroke motions to apply paint at the same speed, same angle and same pressure, from the beginning of the first paint stripe for the nominated distance. The paint stripe therefore shows: [0071] coverage qualities [0072] crispness of the painted edge [0073] rate at which the paint is released [0074] the level of finish relating to brush marks [0075] paint delivery distance [0076] brush performance per side.

[0077] The test criteria are summarised in Table 1 below.

TABLE-US-00001 TABLE 1 Test Criteria Date 11 Mar. 2021 Test number ART01 Test type Robotic Brush Width 63 mm Brush Thickness 20 mm Paint Type Low Sheen Paint Solvent Water Substrate - Material Paper Substrate - Surface Finish High Gloss Brush prep time 10 min soak Cycle Type Painting Cycles (coats) 1 Repeat Tests 0 Coverage area Pre-set program Test Temperature 22? Brush/Roller BRUSH Brush ID Competitor vs HX3 Brush Dip Depth 35 mm Soak Time 30 sec Drip Time 5 sec Application Location 2 (vertical wall) Application Width 63 mm Application Length 750 mm Application Speed 100 mm/s Application Pressure 25 mm Application Angle 30? Number of Strokes 4

[0078] It can be seen in both the single cycle and three cycle test results that the paint brush of the present invention significantly outperformed the conventional paint brush.

[0079] Given the painting motion of the robot was identical in each test, the coverage performance of each brush can be measured by analysing the images to determine the proportion of the test area, within a digitised image of each sample, painted versus not painted (black versus white in the images shown in FIGS. 11 and 12). This analysis shows that the sample paint brush of the present invention achieved a coverage performance of between 75% and 77%. In contrast, most conventional mid-level paint brushes produced a coverage performance of only around 60% to 64%. Only the very best competing paint brushes have achieving up to about 69%. The sample paint brush of the present invention therefore outperformed the very best available prior art paint brush by around 8%. As a reference, medium to low brushware tended to rate between 50%-60% coverage.

[0080] Paint brushes made in accordance with preferred embodiments of the invention have also been found to work surprisingly well when completely new and straight out of the packaging, and do not need much time to build up to an optimum painting level. In this regard, it can be seen in the test of FIG. 12, involving three coats of paint, that the right-hand paint brush (being the preferred embodiment of the present invention) didn't really need the third coat applied; it looked much the same after the second coat had been applied. The third coat simply applied more paint which, in most instances, would be unnecessary. Accordingly, it can be concluded that the paint brush of the present invention spread the paint much more efficiently than the conventional brush.