CA2185318A1 - Log sorter and feeder - Google Patents

Abstract

An apparatus for individually sorting and separating a plurality of generally elongated cylindrical objects of the same or varying diameter and length, the apparatus having an upstream cylindrical object receiving end, and a downstream cylindrical object dispensing end, comprising: (a) a downstream inclined cylindrical object receiving member, the receiving member including a cylindrical object receiving end, and inclined cylindrical objects rolling face which inclines downwardly from an upper end at the receiving end to a lower end, downstream from the receiving end, the inclined receiving member having at its lower end a first restraining member which holds cylindrical objects in parallel and abutting relationship with one another; (b) a cylindrical object pick-up device which fetches one or more cylindrical objects in the first lower end restraining member and conveys the cylindrical objects upwardly upstream along an upwardly inclined surface; (c) a second cylindrical object restraining member located at a top region of the upstream upwardly inclined surface; and (d) a downwardly inclined cylindrical object conveying surface downstream from the second cylindrical object restraining member and proximate to the downstream cylindrical object dispensing end.

Description

LOG SORTER AND FEEDER

FIELD OF THE INVENTION

This invention is directed to an apparatus for single feeding elongated cylindrical objects to a suitable cylindrical object processing apparatus. In one aspect, this invention is directed to a log sorting and feeding apparatus which is capable of sorting logs of variable diameter and feeding the logs one at a time in parallel arrangement to a log processing apparatus.

BACKGROUND OF THE INVENTION

The selection and delivery of individual cylin-drical objects, or selected groups of cylindrical objects such as logs, pipes, and the like, which are generally of elongated cylindrical form, from a group of such objects has in the past presented a substantial and challenging problem. The task of serially separating a cylindrical object from a random stack or group of unaligned cylindri-cal objects of various diameters, lengths and orientations, and aligning them in parallel one at a time and directing them singly to a cylinder handling apparatus has tested and consumed the minds of intelligent inventors over the years.
Such a problem is common in the log handling industry.
Numerous machines and processes have been designed over the years for purportedly efficiently handling a random mix of stacked logs of various diameters and lengths with mixed butts and ends, and arrayed in various directions, and sorting them and aligning them one at a time in a common direction for feeding without interruption in a single layer to a log processing machine, such as a debarker or a chip and saw apparatus.
The following patents disclose various device and systems for processing cylindrical objects and, in particu-lar, logs.

- ' 2185318 U.S. Class U.S. Patent No. Inventor 198/463.5 3,330,401 Ahlstedt 4,624,361 Hollins 4,852,716 Roche 4,911,283 Hollins 5,119,930 Stelter 198/443 4,997,079 Suopajarvi et al.
414/746.4 4,930,616 Lindberg U.S. Patent No. 4,997,079, Suopajarvi et al., discloses a log sorting apparatus which involves two rotating drums. A rapidly rotating drum 5, with a smooth surface, is located at the bottom of a log aperture entry port 18, and moves logs from the bottom layer over to a 15 more slowly rotating larger drum 6, which has a plurality of log retaining members 7 around the surface thereof. The slowly rotating drum 6, with the log retaining members 7, moves the logs in single series to a conveyor belt 15, where they are conveyed away for log processing.
The Suopajarvi et al. apparatus does not disclose a single drum nor a series of parallel shear plates with a log retaining pocket on the top of the shear plates.

U.S. Patent No. 5,119,930, Stelter, discloses a quadrant log feature which comprises a reciprocating quadrant 16. The quadrant 16 lifts a log 26 up a sloping parallel series of radial ribs 34 to a second holding location 40. A series of rotating discs 44 are mounted on 30 a rotating shaft 46, located adjacent the second holding location 40. These allow the log to exit onto an exit conveyer 50. Stelter does not disclose a rotating drum with left arms.

U.S. Patent No. 4,930,616, Lindberg, discloses a rotary log singulator located between a log feeder 12 and an outfeed or discharge station 14. The singulator 10 is comprised of a plurality of rotating drums 16 and a plural-ity of lifting separating bars 18. Lindberg does not show a parallel series of shear plates, with top notches for log retention.

U.S. Patent No. 4,852,716, Roche, discloses a rotating drum 18 which unscrambles logs and conveys them singly down a ramp 20 to a conveying means 22, which transports the logs in a single layer to a stop 24. The stop 24 reciprocates and feeds logs singly onto a debarker conveyer 26. The drum 18 has lugs 36 thereon which grab the logs and move them over the top of the drum 18. Roche does not disclose parallel shear plates or a log retention pocket on the top of the shear plates.
U.S. Patent No. 3,330,401, Ahlstedt, discloses an apparatus for the selection and sidewise delivery of selected sets of long rollable objects of varying diameters from a closely spaced group of such objects, such as logs.
20 A lift arm holds the logs back in an "up" position, and releases one log at a time while in the "down" position.
At the same time, a second log is allowed to lodge in a pocket to retain remaining logs. Ahlstedt does not dis-close a rotating drum with lift arms, or parallel shear 25 plates.

Hollins, in U.S. Patent Nos. 4,624,361 and 4,911,283, discloses a log singulator which uses a parallel series of reciprocating log lift arms to sort and individ-30 ualize logs. Hollins does not disclose a rotating drumwith lift arms.

SUMMARY OF THE INVENTION

The invention is directed to an apparatus for individually sorting and separating a plurality of gen-erally elongated cylindrical objects of the same or varying diameter and length said apparatus having an upstream cylindrical object receiving end, and a downstream cylin-drical object dispensing end, comprising: (a) downstream inclined cylindrical object receiving means, said receiving means including a cylindrical object receiving end, and inclined cylindrical objects rolling face which inclines downwardly from an upper end at the receiving end to a lower end, downstream from the receiving end, the inclined receiving means having at its lower end a first restraining means which holds cylindrical objects in parallel and abutting relationship with one another; (b) a cylindrical object pick-up device which fetches one or more cylindrical objects in the first lower end restraining means and conveys the cylindrical objects upwardly upstream along an upwardly inclined surface; (c) a second cylindrical object restraining means located at a top region of the upstream upwardly inclined surface; and (d) a downwardly inclined cylindrical object conveying surface downstream from the second cylindrical object restraining means and proximate to the downstream cylindrical object dispensing end.

The cylindrical object pick-up device may be a rotating cylinder which can have its axis of rotation disposed parallel to the length of the cylindrical objects.
The cylinder can have spatially disposed around the circumference thereof a series of cylindrical object lift arms. The series of cylindrical object lift arms can be arranged in spaced rows aligned with the axis of the cylinder.

The upstream upwardly inclined surface can comprise at least two parallel spaced shear plates which can extend perpendicularly to the axis of the cylinder and partially around the top circumference of the cylinder.
The downstream downwardly inclined surface can comprise at least two parallel spaced shear plates which can extend perpendicular to the axis of the cylinder and partially around the downstream side of the cylinder. The at least two upstream shear plates and the at least two downstream shear plates can be aligned and contiguous with one another.

The second cylindrical object restraining means can be comprised of axially aligned open top depressions located at a junction between the tops of the at least two upwardly inclined upstream shear plates and the at least two downwardly inclined downstream shear plates.

The elevation of the top profile of the at least two upstream shear plates and the at least two downstream shear plates, the depth of the depressions between the at least two upstream shear plates and the at least two downstream shear plates, and the elevation of the rows of lift arms can be engineered so that if two adjacent cylin-drical objects have a total diametrical width that is larger than a predetermined distance, one of the two cylindrical objects will be pushed upstream down the at least two upstream shear plates to a following row of lift arms.

The cylinder can be a hollow drum, which can have disposed around the circumference thereof at least two rows of parallel, and axially aligned, lift arms which project radially from the circumference of the drum.

The inclined cylindrical object receiving means can be comprised of at least two spaced parallel skid plates that can be perpendicular to the axis of the cylin-der, the downstream ends of which skid plates can align respectively with the upstream bases of the at least two upwardly inclined upstream shear plates.

21853~8 -The at least two upstream upwardly inclined parallel plates, the at least two downstream inclined parallel shear plates, and the at least two skid plates can be respectively formed from one piece of material.

A cylindrical object feeding mechanism can be located at an upstream receiving end of the skid plates and can contact cylindrical objects one at a time and convey them to an upstream end of the at least two skid plates.
The upstream cylindrical objects contacting faces of the rows of lift arms can be concave curved.

The apparatus can comprise at least five upstream skid plates, at least five upstream upwardly inclined shear plates, at least five downstream downwardly inclined shear plates in alignment with one another, and ten rows of lift arms disposed spatially around the circumference of the cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate specific embodiments of the invention, but which should not be construed as restricting the spirit or scope of the invention in any way:

Figure 1 illustrates a perspective view of the log sorter and feeder, taken from the perspective of the log deck and skid plate.
Figure 2 illustrates a perspective view of the log sorter and feeder, taken from the perspective of the down slope side and log conveyor.

Figure 3 illustrates a perspective view of the side of the log sorter and feeder.

21853~8 -Figure 4 illustrates a plan view of the log sorter and feeder.

Figure 5 illustrates a side elevation view of the log sorter and feeder.

Figures 6, 7, 8, 9 and 10 illustrate in sequence side elevation views of the manner in which the log sorter and feeder handles logs of different diameter and sorts them into single logs for delivery one at a time to a log conveyor.

DETAILED DESCRIPTION OF SPECIFIC
EMBODIMENTS OF THE INVENTION
This invention relates to a reliable mechanical device which is capable on a continuous basis of selecting logs of varying diameter and length from a group of random logs and efficiently single feeding the logs in parallel orientation to a log processing apparatus.

According to the method and apparatus of the invention, logs are taken individually in parallel orienta-tion from a deck or log unscrambler and moved onto parallel sloped skid plates of the log sorter and feeder. The skid plates permit the logs to roll downwardly in a single layer until they abut either the log head or a skid plate pocket formed at the base of the skid plate. The skid plate pocket is specially contoured to hold back small logs or conversely allow larger logs to roll ahead. The log feeder has a rotating drum with a series of specifically shaped circumferentially extending lift arms located in linear rows around the peripheral cylindrical surface of the drum.
These rows of lift arms rotate with the drum about the axis of the drum and serially pick one or more logs from the skid plate pocket at the bottom of the skid plate and carry 21853~8 -them on parallel shear plates up and over the top of the drum.

The specifically designed series of parallel shear plates are positioned at spaced intervals along the length of the drum. The profile of the shear plates is specifically designed with increasing elevation so that if two logs are picked up from the skid plate pocket by the rows of lift arms, the first log contacts the shear plate which in turn applies an outward force against the second log. The second log is then forced radially outwardly as the row of lift arms move the second log upwardly around the increasing elevation of the profile of the parallel series of skid plates. Ultimately, the profile of the parallel series of shear plates increases to an elevation whereby the second log drops backwardly over the tops of the row of lift arms and returns by gravity to the skid plate pocket. By this procedure, the first log is singu-lated and proceeds on the shear plates over the top of the drum to a specifically designed pocket which is formed by a linear alignment of curved depressions in the tops of the parallel series of shear plates.

The shear plate pocket is designed to hold a log from tumbling off the curved tops of the parallel series of shear plates, in either direction, and thereby possibly landing on top of a log in the log processing apparatus that has been previously selected and before the previously selected log has had a chance to be carried away by the log conveyer. The log remains in the shear pocket until the following row of lift arms reaches the log and moves it to a position where it slides down the down slope of the down-stream side of the parallel series of shear plates. The log then proceeds to roll onto a log conveying apparatus and is carried away for processing.

-g The apparatus of the invention will now be described in association with the drawings. Figure 1 illustrates a perspective view of the log sorter and feeder, taken from the perspective of the upstream log deck and skid plate. As can be seen in Figure 1, the log sorter and feeder 2 receives a plurality of logs 4 which are aligned in parallel fashion on a deck 6. A log feeding wheel 8 which is constructed of a parallel series of notched discs 9 mounted on an axle 11 aligned with the logs 4 moves the logs 4 one at a time in the direction of a downwardly sloping parallel series of spaced skid plates 10, which are arranged at right angles to the direction of the logs 4. A skid plate pocket 12 (not readily seen in Figure 1, but see Figure 5) is constructed at the bottom end of the skid plates 10 and receives and holds logs 4 at the downstream side of the parallel series of skid plates 10 .

A large cylindrical drum 14 with an axis which is parallel to the logs 4 rotates counterclockwise (as seen in Figure 1) about an axle 16, one end of which is mounted in bearings 18. While not visible in Figure 1, the opposite end of the axle 16 is also mounted in a corresponding bearing 18. The drum 14, axle 16 and set of bearings 18 are mounted on a support frame 20.

The cylindrical surface of the drum 14 is equipped around its circumference with a spaced series of parallel lift arms 22 arranged in rows along the axial length of the surface of the drum 14. These lift arms 22 are specially designed in contour and elevation to have a curved log contacting profile on the front side, and an elevation of a specific height above the circumference of the drum 14, and the top elevation of the curved series of shear plates 24, which are discussed below.

A parallel spaced series of shear plates 24 are aligned with respective skid plates 10 at right angles to the length of the logs and extend in parallel over the top surface of the drum 14 on both the upstream and downstream 5 sides of the drum 14. The rows of lift arms 22 are posi-tioned so that they are arranged in pairs on either side of the respective parallel series of shear plates 24. The top region of each of the parallel series of shear plates 24 has formed therein a specially engineered shear plate pocket 26. The pockets 26 and the top of each shear plate 24 are linearly aligned with one another so that they hold a log as shown in Figure 1. Each pocket 26 which has a uniform depth relative to the top elevation of the series of shear plates 24, at the top region of the drum 14. The 15 top elevations of the series of pairs of lift arms 22 are engineered so that the lift arms 22 extend a predetermined elevation above the tops of the shear plates 24 and the row of pockets 26.

The parallel series of shear plates 24 are slanted downwardly on the downstream side so that a log 4 that is being held in the pocket 26, when urged by the following row of lift arms 22, drops downwardly by gravity onto a log conveyer 30. The downstream side of the shear 25 plates has been designated 28. The log conveyer 30 then conveys the log 4 away to a typical debarker or log pro-cessing machine.

Figure 2 illustrates a perspective view of the 30 log sorter and feeder, taken from the perspective of the down slope side and log conveyer. Figure 3 illustrates a perspective view of the side of the log sorter and feeder.

Figures 2 and 3 provide a better view of features 35 such as the parallel row of skid plates 10, the shear plate pocket 26, formed by the depressions in the tops of the parallel row of shear plates aligned with the skid plates 2lss3la -10, the downslope 28 of the shear plates 24, and the rela-tive elevational relationship between the tops of the row of lift arms 22, at the top of their travel, the tops of the row of shear plates 24 and the depth of the shear 5 pocket 26 formed in the tops of the row of shear plates 24.

Figure 4 illustrates a plan view of the log sorter and feeder 2. As seen in Figure 4, the drum 14 is rotationally mounted on the frame 20 perpendicular to the direction of travel of the log with the axle 16 axially disposed within the drum 14 and mounted in bearings 18 at each side of the frame 20. Axial aligned rows of lift arms 22 are disposed at parallel intervals around the circumfer-ence of the drum 14. The drum 14 is rotationally driven by 15 a drive 32, which can be a motor, or a linkage to some other power source. As also seen in Figure 4, the series of shear plates 24 are arranged in parallel and spaced alignment perpendicular to the axis of rotation of the drum 14 and in spaces provided between the rows of lift arms 22 20 which are arranged parallel to the axis of the drum 14.
The parallel and spaced series of skid plates 10 are shown at the top of Figure 4. These skid plates 10 are aligned with the corresponding parallel series of shear plates 24.
Indeed, each skid plate 10 can be formed with the corre-25 sponding shear plate 24 as one unit.

Figure 5 illustrates a side elevation view of thelog sorter and feeder 2. As can be seen in Figure 5, the upstream skid plate 10 has a smooth linear downward slope 30 in the direction of the drum 14. At the base of the downward slope of the skid plate 10, there is formed a specially contoured skid plate pocket 12. This skid plate pocket 12 stops the advancement of logs which have rolled down the top surface of the skid plate 10. As also can be 35 seen in Figure 5, the shear plate 24 is profiled so that it extends from the upstream side of the drum 14 to the downstream side of the drum 14, as indicated by the rotational arrow on the drum 14. The lift arms 22 are spatially arranged around the circumference of the drum 14 and project radially outwardly. As seen in Figure 5, there are ten rows of lift arms 22 located every 30 degrees 5 around the circumference of the drum 14. The number of rows of lift arms 22 can be varied as required for specific applications. The front, that is, the log contacting surfaces of the respective lift arms 22, are curved to accommodate the curved configuration of the surface of a log.

The top profile of the shear plate 24 is designed so that it increases radially outwardly relative to the surface of the drum 14, on the upstream side of the drum 15 14, until a specific elevation, relative to the top elev-ation of the lift arm 22, is reached. At the top of the shear plate 24, a shear plate pocket 26, of a predetermined depth and circular shape, is formed in the top region of the shear plate 24. The top profile of the downstream side 20 of the shear plate 24 is sloped downwardly to enable logs to be rolled downwardly thereon, when they are pushed by the respective lift arm 22 from the pocket 26.

Figures 6, 7, 8, 9 and 10 illustrate in sequence 25 side elevation views of the manner in which the log sorter and feeder handles logs of different diameter and sorts them into single logs for delivery one at a time to a log conveyer (not shown). Figure 6 illustrates five logs of different diameters located on the top surface of the skid plate 10. Two logs of relatively small diameter, that is, logs 34 and 36, are located at the bottom of the skid plate 10 in the skid plate pocket 12. A log 38, of diameter considerably larger than logs 34 and 36, is next in line on the skid plate 10. A log 40, of diameter larger than logs 3S 34 and 36, but smaller than log 38, is next in line on the upstream side of skid plate 10. Finally, a log 42, of diameter larger than any of the other logs, is located at a higher upstream elevation on the top surface of the skid plate 10.

Figure 7 is subsequent in time to Figure 6 and 5 illustrates the position of the drum 14 after it has rotated roughly 45 to 50 degrees from the position illus-trated in Figure 6. As seen in Figure 7, lift arm 22 has picked up the two small diameter logs 34 and 36 and moved them part way up the upstream surface of shear plate 24.
Meanwhile, relatively large diameter log 38 has been picked up by the following lift arm 22.

Figure 8 is subsequent in time to Figure 7 and illustrates the position of the drum 14 after it has 15 rotated clockwise a further 10 or 15 degrees beyond the position illustrated in Figure 7. At that point, the elevation of the top profile of the shear plate 24 has increased to the level where it is almost as high as the top elevation of lift arm 22. Then the first log 34 20 remains on the front side of lift arm 22 while the second log 36 tumbles rearwardly over the top of lift arm 22, and falls back to a position where it is stopped by log 38, which is being raised by the following lift arm 22.

Figures 9 and 10 are in sequence and subsequent in time to Figure 8 and illustrates the position of the drum 14 after it has rotated clockwise, first as seen in Figure 9, a further few degrees compared to the position shown in Figure 8, and then a further 20 to 25 degrees as 30 seen in Figure 10. As can be seen in Figure 9, small diameter log 34 has dropped forwardly into pocket 26 where it is held. Meanwhile, logs 36 and 38 have been advanced slightly up shear plate 24 by following lift arm 22. As the drum 14 continues to rotate in a clockwise direction, 35 lift arm 22 will contact small diameter log 34 in shear pocket 26, and push it over the top of shear plate 24 so that it drops by gravity down the downstream slope 28 of shear plate 24, as seen in Figure 10. Meanwhile, mid-diameter log 38, and small diameter log 36 are being raised by the following lift arm 22 to a point where the top of the upstream side of the shear plate 24 will be reached.
5 At that point, the difference in elevation between the top of shear plate 24 and the top of lift arm 22 will be sufficiently small that small diameter log 36 will force mid-diameter log 38 radially upwardly and log 36 will be moved forwardly into position into the shear plate pocket 10 26. Meanwhile, raised mid-size diameter log 38 will tumble rearwardly and downwardly over the top of lift arm 22, as seen in Figure 10, until it is stopped by following log 40.
The log sorting and singulating procedure then continues.

Figures 6 through 10 illustrate in sequence how the log sorter and feeder 2 according to the invention is able to handle logs of significantly different diameters, and separate them from one another, and feed them individ-ually to a log conveyer 30. One key to the successful 20 operation of the log sorter and feeder 2 according to the invention is the precise engineering of the relative dimensions of the lift arms 22, the top profile of the shear plate 24 and the size and depth of pocket 26 so that logs of different diameters will be moved either forwardly, 25 one at a time, into the shear plate pocket 26, or tumble rearwardly and downwardly over the top of the respective lift arms 22, for engagement with and lifting by a follow-ing lift arm 22.

As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be 35 construed in accordance with the substance defined by the following claims.

Claims (15)

1. An apparatus for individually sorting and separating a plurality of generally elongated cylindrical objects of the same or varying diameter and length said apparatus having an upstream cylindrical object receiving end, and a downstream cylindrical object dispensing end, comprising:
(a) downstream inclined cylindrical object receiving means, said receiving means including a cylindrical object receiving end, and inclined cylindrical objects rolling face which inclines downwardly from an upper end at the receiving end to a lower end, downstream from the receiving end, the inclined receiving means having at its lower end a first restraining means which holds cylindrical objects in parallel and abutting relationship with one another;
(b) a cylindrical object pick-up device which fetches one or more cylindrical objects in the first lower end restraining means and conveys the cylindrical objects upwardly upstream along an upwardly inclined surface;
(c) a second cylindrical object restraining means located at a top region of the upstream upwardly inclined surface; and (d) a downwardly inclined cylindrical object conveying surface downstream from the second cylindrical object restraining means and proximate to the downstream cylindrical object dispensing end.

2. An apparatus as claimed in claim 1 wherein the cylindrical object pick-up device is a rotating cylinder which has its axis of rotation disposed parallel to the length of the cylindrical objects.

3. An apparatus as claimed in claim 2 wherein the cylinder has spatially disposed around the circumference thereof a series of cylindrical object lift arms.

4. An apparatus as claimed in claim 3 wherein the series of cylindrical object lift arms are arranged in spaced rows aligned with the axis of the cylinder.

5. An apparatus as claimed in claim 4 wherein the upstream upwardly inclined surface comprises at least two parallel spaced shear plates which extend perpendicularly to the axis of the cylinder and partially around the top circumference of the cylinder.

6. An apparatus as claimed in claim 5 wherein the downstream downwardly inclined surface comprises of at least two parallel spaced shear plates which extend perpendicular to the axis of the cylinder and partially around the downstream side of the cylinder.

7. An apparatus as claimed in claim 6 wherein the at least two upstream shear plates and the at least two downstream shear plates are aligned and contiguous with one another.

8. An apparatus as claimed in claim 7 wherein the second cylindrical object restraining means is comprised of axially aligned open top depressions located at a junction between the tops of the at least two upwardly inclined upstream shear plates and the at least two downwardly inclined downstream shear plates.

9. An apparatus as claimed in claim 8 wherein the elevation of the top profile of the at least two upstream shear plates and the at least two downstream shear plates, the depth of the depressions between the at least two upstream shear plates and the at least two downstream shear plates, and the elevation of the rows of lift arms are engineered so that if two adjacent cylindrical objects have a total diametrical width that is larger than a predetermined distance, one of the two cylindrical objects will be pushed upstream down the at least two upstream shear plates to a following row of lift arms.

10. An apparatus as claimed in claim 2 wherein the cylinder is a hollow drum, which has disposed around the circumference thereof at least two rows of parallel, and axially aligned, lift arms which project radially from the circumference of the drum.

11. An apparatus as claimed in claim 7 wherein the inclined cylindrical object receiving means is comprised of at least two spaced parallel skid plates that are perpendicular to the axis of the cylinder, the downstream ends of which skid plates align respectively with the upstream bases of the at least two upwardly inclined upstream shear plates.

12. An apparatus as claimed in claim 11 wherein the at least two upstream upwardly inclined parallel plates, the at least two downstream inclined parallel shear plates, and the at least two skid plates are respectively formed from one piece of material.

13. An apparatus as claimed in claim 11 wherein a cylindrical object feeding mechanism is located at an upstream receiving end of the skid plates and contacts cylindrical objects one at a time and conveys them to an upstream end of the at least two skid plates.

14. An apparatus as claimed in claim 10 wherein the upstream cylindrical objects contacting faces of the rows of lift arms are concave curved.

15. An apparatus as claimed in claim 11 comprising at least five upstream skid plates, at least five upstream upwardly inclined shear plates, at least five downstream downwardly inclined shear plates in alignment with one another, and ten rows of lift arms disposed spatially around the circumference of the cylinder.