High speed sealant strip application

Abstract

An applicator is disclosed for applying sealant to a moving substrate. The applicator includes a wheel having a periphery. A plurality of spaced apart footprints extends around the periphery of the wheel and each footprint has a sealant receiving feature. A reservoir is provided for containing a supply of sealant to be applied to the moving substrate. The wheel is rotatably mounted at least partially in the reservoir such that as the wheel rotates, each of the spaced apart footprints repeatedly moves through a supply of sealant in the reservoir to pick up a charge of sealant, around one side of the wheel toward the moving substrate, adjacent the moving substrate to transfer the sealant charge to the substrate, and around the other side of the wheel back toward the supply of sealant. At least one stop is formed on each of the footprints for inhibiting sealant picked up by the footprint from being urged rearwardly on the footprint by high speed rotation of the wheel. A backstop may be formed at a trailing end of each footprint and mid-stops may be formed between a leading end of each footprint and the trailing end.

Claims

1. An applicator for applying sealant to a moving substrate, the applicator comprising: a wheel having a periphery; a plurality of spaced apart footprints extending around the periphery of the wheel, each footprint having a leading end, a trailing end, and a sealant receiving feature; a reservoir for containing a supply of sealant to be applied to the moving substrate; the wheel being rotatably mounted at least partially in the reservoir such that each of the spaced apart footprints repeatedly moves through a supply of sealant in the reservoir to pick up a charge of sealant, around one side of the wheel toward the moving substrate, adjacent to the moving substrate to transfer the sealant charge to the moving substrate, and around the other side of the wheel back toward the supply of sealant; and a structure on each of the footprints for inhibiting sealant picked up by the footprint from being urged rearwardly toward the trailing edge of the footprint by high speed rotation of the wheel, wherein the structure comprises a backstop extending across each footprint at the trailing end thereof.

2. An applicator as claimed in claim 1 wherein the structure for inhibiting sealant from being urged reawardly comprises at least one mid-stop extending across each footprint intermediate the leading end of the footprint and the trailing end of the footprint.

3. An applicator as claimed in claim 2 wherein the structure for inhibiting sealant from being urged reawardly further comprises a backstop extending across each footprint at the trailing end of the footprint.

4. An applicator as claimed in claim 3 wherein the at least one mid-stop comprises at least two mid-stops.

5. An applicator as claimed in claim 3 wherein the at least one mid-stop comprises at least three mid-stops.

6. An applicator as claimed in claim 1 wherein the sealant receiving feature comprises a depressed region extending along each footprint from the leading end of the footprint to the trailing end of the footprint.

7. An applicator as claimed in claim 6 wherein each footprint has opposing side edges and further comprising a first upstanding side wall extending along one side edge of each footprint and a second upstanding wall extending along the opposite side edge of each footprint, the depressed region being defined between the first and second upstanding side walls.

8. An applicator as claimed in claim 7 wherein the structure for inhibiting sealant from being urged rearwardly comprises a third upstanding wall spanning across the depressed region at the trailing end of the footprint, the third upstanding wall forming a backstop.

9. An applicator as claimed in claim 8 further comprising a fourth upstanding wall spanning across the depressed region between the leading end of the footprint and the trailing end of the footprint, the fourth upstanding wall forming a mid-stop.

10. An applicator as claimed in claim 9 further comprising multiple upstanding walls spanning across the depressed region between the leading end of the footprint and the trailing end of the footprint, each of the multiple upstanding walls being spaced from other upstanding walls and each forming a mid-stop between the leading and trailing ends of the footprint.

11. An applicator as claimed in claim 6 wherein the depressed region has a substantially flat bottom.

12. An applicator as claimed in claim 6 wherein the depressed region has a curved bottom.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a side elevation showing in simplified form a prior art sealant strip application system illustrating problems that arise with attempts to run at high line speeds.

(2) FIG. 2 is a perspective view of a single footprint of a prior art sealant strip application wheel.

(3) FIG. 3 is a perspective view showing one embodiment of a single footprint of a sealant strip application wheel according to principles of the invention.

(4) FIG. 4 is a perspective view showing an alternate embodiment of a single footprint of a sealant strip application wheel according to principles of the invention.

DETAILED DESCRIPTION

(5) Reference will now be made in more detail to the attached drawing figures, wherein like reference numerals indicate like parts where appropriate throughout the views. FIG. 1 is a highly simplified schematic drawing of a typical prior art sealant applicator disposed along a shingle manufacturing line and illustrates problems with the prior art at higher line speeds. The sealant applicator 11 is disposed beneath a web of shingle stock 12 that is being moved in a processing direction 13 at a predetermined line speed. In FIG. 1, the predetermined line speed is a high speed that is higher than a typical shingle line speed commonly used in the past, and may be significantly higher.

(6) The sealant applicator 11 includes a reservoir 14 that contains a supply of sealant 16. The sealant may be an asphalt, and adhesive, or any other liquid material intended to be applied to the shingle stock above. An applicator wheel 17 is mounted at least partially within the reservoir for rotation about a horizontal axis that extends perpendicular to the direction 13. The applicator wheel 17 is formed with a plurality footprints 18 extending around the periphery of the applicator wheel 17. The footprints are separated by gaps 19. The gaps 19 extend inwardly to merge with cutouts 21 in the applicator wheel that function to collect and shed excess sealant that may fall through the gaps 19. The cutouts 21 may be circular, U-shaped, or otherwise shaped as desired.

(7) A drive mechanism (not shown) is coupled to the applicator wheel and is controlled to rotate the wheel in direction 22 at a desired rate. The desired rate preferably is such that the surface speed of the footprints 18 is substantially the same as the line speed at which the shingle stock 12 moves in the processing direction 13. As the applicator wheel rotates, the footprints 18 are moved through the supply of sealant 16 in the reservoir 14 and each footprint picks up a charge of sealant (e.g. charge 23). The charges of sealant are then transported by the footprints around and up toward the moving shingle stock 12. At the top of the applicator wheel, the footprints engage the moving shingle stock and the charges of sealant carried by the footprints are transferred to the shingle stock. This, in turn, creates a strip of sealant along the shingle stock characterized by dashes of sealant separated by spaces between the dashes, i.e. a self-seal strip.

(8) As mentioned, FIG. 1 depicts operation of the prior art sealant applicator wheel at a high speed and illustrates problems that have been found to arise at such high speed operation with maintaining the sealant in place on the footprints. It should be understood that dimensions and configurations of sealant are exaggerated in FIG. 1 for a clearer understanding of these problems. As the applicator wheel rotates at a high rate, each footprint moves through the supply of sealant 16 and picks up a charge of sealant to be applied to the shingle stock above. Each charge is then carried around and up by its footprint until it is applied to the shingle stock. However, since the prior art applicator wheel in FIG. 1 is rotating at a high speed in this example, each charge of sealant is gradually urged rearwardly in the groove of the footprint. Some of the charge may well slide off of the trailing edge of the footprint before the footprint reaches the shingle stock.

(9) This phenomenon is illustrated in FIG. 1. The sealant charge 23 is seen to be substantially evenly distributed along its footprint just after having been picked up from the sealant supply 16. Sealant charge 24, which was picked up slightly earlier than sealant charge 23, is being urged by the high speed rotation of the wheel 17 slightly rearwardly. Sealant charge 25 has been urged even more rearwardly and the trailing end of this charge is beginning to slide off of the trailing end of the footprint. As a consequence, the sealant charge 25 is beginning to become unevenly distributed along the footprint with relatively more sealant near the leading edge of the footprint and relatively less sealant near the trailing edge of the footprint. The phenomenon continues to worsen for the footprints that have been carried further around and up. Sealant charges 26, 27, 28, and 29 are seen to be progressively more misshaped and unevenly distributed as more sealant slides rearwardly and off the trailing edge of the footprint.

(10) Sealant charge 31 has been carried by its footprint into contact with the moving shingle stock above and is being transferred to the shingle stock to form a sealant dash. However, because the charge 31 has become misshapen during its journey around and up, the resulting dash on the shingle stock is applied unevenly. For instance, there may be an excess of sealant at the beginning of the sealant dash and comparatively little sealant at the end of the sealant dash. This is illustrated at 32 in FIG. 1. In addition, applied sealant dashes can have ridges that extend down the length of the dash and/or bridging between dashes can occur due to the sealant trailing behind the footprints within the gaps that separate them. At higher and higher line speeds, the quality of the applied self-seal strip degrades and ultimately becomes unacceptable.

(11) FIG. 2 shows the top of a typical prior art footprint found on sealant applicator wheels. The footprint 18 has a first upstanding side wall 36 and a second upstanding side wall 37 extending along the sides of the footprint. The first and second upstanding side walls define a depressed region, in this case a groove, between the walls. Sealant is picked up in the groove as the footprint moves through the sealant supply at the bottom of the reservoir. The first and second walls 36 and 37 help prevent the sealant from spilling over the sides of the footprint as it is carried around and up with the rotating applicator wheel. As mentioned above, however, high speed operation of the sealant wheel progressively urges sealant charge rearwardly and some of the charge may slide off of the trailing edge 20 of the footprint.

(12) FIG. 3 shows a single footprint of a sealant applicator wheel that incorporates principles of the present invention in one preferred embodiment. The footprint 18 is defined between gaps 19 on the periphery of the sealant applicator wheel. A first upstanding side wall 39 extends along one side of the footprint and a second upstanding side wall 41 extends along the opposite side of the footprint. The first and second upstanding side walls define between them a groove 42 for receiving sealant to be applied to a moving web of shingle stock. A third upstanding wall 44 spans the trailing end of the groove 42 and forms a backstop 43 at the trailing end of the groove. In the embodiment illustrated in FIG. 3, the backstop is arcuate in shape to apply sealant dashes with curved ends; however, it may just as well be straight or configured with some other shape as desired.

(13) During operation of the sealant applicator wheel 17 at high speeds in high speed shingle manufacturing, each footprint 18 of FIG. 3 picks up a charge of sealant as previously described. As the sealant is carried around and up toward the moving shingle stock, the backstop 43 formed by the third upstanding wall 44 inhibits the sealant from sliding off the trailing end of the groove 42. This, in turn, helps to maintain a more even distribution of the sealant charge along the length of the footprint. When the footprint of FIG. 3 contacts the moving shingle stock at the top of its travel, the more evenly distributed charge of sealant is transferred to the shingle stock. This forms a dash of sealant on the shingle stock that is more consistent, more fully formed, and that exhibits better performance and more consistent performance when shingles are ultimately installed on a roof deck. Further, the entire self-seal strip applied to the shingles is more uniform and bridging between sealant dashes caused by sealant in the gaps between footprints is greatly reduced or eliminated.

(14) FIG. 4 shows a single footprint of a sealant applicator wheel 17 that incorporates principles of the present invention in an alternate preferred embodiment. The footprint 18 is defined between gaps 19 on the periphery of the sealant applicator wheel 17. A first upstanding side wall 46 extends along one side of the footprint and a second upstanding side wall 47 extends along the opposite side of the footprint. The first and second side walls define between them a depressed region, in this case a trough, for picking up sealant to be applied to a moving web of shingle stock. In this embodiment, the trough has a curved shape instead of the flat shape of the groove of FIG. 3. In practice, the depressed region can be any desired shape as dictated by application specific demands.

(15) A third upstanding wall 48 spans the trailing end of the trough and forms a backstop 56 at the trailing end. A fourth upstanding wall 49 spans the trough ahead of the wall 48 and forms a first mid-stop 57. The third and fourth upstanding walls define between them a rear trough section 54 in the trailing portion of the footprint. Similarly, a fifth upstanding wall 51 spans the trough ahead of the fourth upstanding wall 49 and defines a second mid-stop 58. The fourth and fifth upstanding walls 49 and 51 define between them an intermediate trough section 53. A forward trough section 52 is formed ahead of the fifth upstanding wall and terminates at the leading end of the footprint.

(16) During operation of the sealant applicator wheel 17 at high speeds in high speed shingle manufacturing, each footprint 18 of FIG. 4 picks up a charge of sealant as previously described. Part of the charge is contained in the forward trough section 52, part is contained in the intermediate trough section 53, and part is contained in the rear trough section 54. As the sealant is carried around and up toward the moving shingle stock at high speed, the backstop 56 formed by the third upstanding wall 48 inhibits the sealant in the rear trough section 54 from being urged rearwardly off the trailing end of the footprint 18. Similarly, the first mid-stop 57 contains the sealant in the intermediate trough section 53 and inhibits it from being urged rearwardly by the high speed rotation of the wheel. And, the second mid-stop 58 inhibits sealant in the forward trough section 52 from being urged rearwardly as the applicator wheel rotates.

(17) This, in turn, helps to maintain an even distribution and consistent shape of the sealant charge along the length of the footprint. When the footprint contacts the moving shingle stock at the top of its travel, the more evenly distributed and more consistently shaped charge of sealant is transferred to the shingle stock. This forms a dash of sealant on the shingle stock that is more consistent, more fully formed, and that exhibits higher performance when shingles are ultimately installed on a roof deck. Further, the entire self-seal strip applied to the shingles is more uniform and bridging between sealant dashes caused by sealant in the gaps between footprints is greatly reduced or eliminated.

(18) The invention has been described and exemplified herein in terms of preferred embodiments and methodologies considered by the inventor to represent the best modes of carrying out the invention. It will be understood, however, that a wide gamut of additions, deletions, and modifications, both subtle and gross, might well be made by skilled artisans without departing from the spirit and scope of the invention. The scope of the invention is not to be determined by the examples presented and described herein, but rather is delineated only by the claims hereof.