Method for wrapping firework shells

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates broadly to apparatus for wrapping spherical objects. More particularly, this invention relates to an apparatus for wrapping tape about a spherical aerial firework shell.

2. State of the Art

Aerial firework shells generally include a shell portion containing an arrangement of bursting charge and stars, and a fuse extending from outside the shell to the interior thereof to ignite the bursting charge and stars. The stars are pellets which burn in color and provide the spectacular display of the firework. The bursting charge is generally black powder and provides the force which disperses the stars when the firework shell is shot.

There are generally two types of aerial firework shells: cylinder shells and spherical shells. Cylinder shells are originally Italian in design and contain the bursting charge and stars in a cylindrical casing. Spherical shells are originally Chinese in design and contain the bursting charge and stars in a spherical casing. Spherical shells generally come in one of several standard sizes, diameters of six inches, eight inches, ten inches, twelve inches, and sixteen inches, although other sizes can be constructed. It is the spherical shell which is most common at large professional firework displays, such as seen on the fourth of July.

In the prior art, spherical firework shells are made entirely by hand. Two hemispherical shell portions are each filled with bursting charge and stars and then brought together to form a sphere. A single piece of tape is manually applied to the sphere to temporarily maintain the integrity of the sphere. One of the shell portions is provided with a fuses which extends from outside the portion to the interior of the shell adjacent the bursting charge. The sphere is then evenly wrapped in individual strips of kraft paper, each generally one to two inches wide and having a length which is substantially the diameter of the sphere. The kraft paper is applied to the sphere using a paste, in a manner similar to papier-maché. The paper wrapping integrates the shell and provides a casing having the necessary structural integrity to permit the shell to be shot from a cannon and not allow the shell to explode until the lit fuse extending between the exterior of the casing and the interior black powder reaches the black powder. To that point, when the shell is wrapped, care is taken to wrap around the fuse, and not cover or otherwise inhibit the function of the fuse. The wrapping of the casing must be very evenly applied in thickness for the shell to explode in a substantially uniform spherical display, as desired. In order that the pasted kraft paper strips should have the required structural integrity, typically forty layers or more of the paper strips are provided about the shell to form a sufficiently strong outer casing.

This paper wrapping process is very labor intensive, requiring hours of manual work for small shells, and days of work for the largest shells. Moreover, the wrapping can be extremely dangerous as the bursting charge is highly combustible. Unfortunately, due to the labor costs, the job of firework manufacture has typically fallen on women and children working under unsafe conditions in economically depressed areas. Widespread disregard for industrial safety and lax enforcement of existing laws lead to frequent deadly accidents in such areas. Recent deaths in China have highlighted the problem. On Mar. 20, 2001, two children were killed in rural China in an explosion at an illegal fireworks factory. Just days before, on Mar. 7, 2001 an explosion at a school in China where children were forced to make fireworks in classrooms killed at least 42 people, mostly children.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a spherical firework shell wrapping system which minimizes human contact with the shell.

It is another object of the invention to provide a system which automatically wraps a spherical firework shell.

It is a further object of the invention to provide a system which evenly wraps a shell of a spherical firework to provide a desirable casing for the firework shell.

It is an additional object of the invention to provide a firework shell wrapping system which is relatively safe to use.

It is also an object of the invention to provide a wrapping system which can evenly wrap spherical objects other than firework shells.

In accord with these objects, which will be discussed in detail below, an apparatus for wrapping fireworks shells is provided and includes a base provided with preferably three support rollers configured to support a spherical firework shell thereon, stepper motors coupled to two of the rollers, a computer coupled to the stepper motors to control the movement of the stepper motors and thereby control the angular rotation of the shell on the rollers, and a dispenser assembly which dispenses continuous-feed tape for wrapping the shell and applies and presses the tape to the shell as the shell is rotated on the rollers. The computer instructs the stepper motors to systematically, at times, rotate the rollers at relatively different speeds, such that a shell on the rollers is subjected to angular rotation and the tape is evenly applied to all portions of the shell such that the tape forms a very even casing of the shell. Additional containment rollers are preferably provided to contain a spherical shell as it is rotated on the support rollers.

In order to accommodate different sizes of spherical shells, different apparatus may be particularly configured for specific sizes of shells: the spacing of the rollers and the height of the applying and pressing components of the dispenser assembly are based upon shell size. As an alternative, an embodiment of an adjustable apparatus in which the roller spacing and the height of the applying and pressing components are both adjustable in order to accommodate shells of different sizes in a single apparatus is also provided.

In operation, a shell is initially assembled by hand from two shell half portions, each provided with the bursting charge and stars, into a sphere. A single piece of tape is manually applied to the sphere to temporarily maintain the integrity of the sphere. Thus far, the assembly is performed in the conventional manner with one exception. No fuse is provided in the sphere. Rather, according to an aspect of the invention, at the fuse hole, a small marker such as a magnet is fixed, for example, with a piece of tape.

Then, according to the invention, the spherical shell is provided on the rollers, and tape from the dispenser is contacted with a portion of the sphere and pressed thereto such that it adheres to the shell. The stepper motors are then activated by the computer to rotate the shell in a pattern which applies multiple layers of tape relatively evenly about the shell. The wrapping is considered complete when sufficient tape in a sufficiently even application is present to form the desired casing.

After the shell is wrapped, a suitable device is used to locate the marker for the fuse. For example, if the marker is a magnet, iron filings can be placed on the shell to locate the marker. The casing is then carefully cut at the marker location to remove the marker, expose the fuse hole, and a fuse is fed through the casing and into the shell and sealed with epoxy to complete the firework.

With the apparatus of the invention, the time for wrapping fireworks shells is greatly reduced to minutes, rather than the hours or days of the prior art. Moreover, once started, the apparatus can run substantially unassisted and therefore provides a much safer method of manufacture than the completely handmade method.

It will be further appreciated that the wrapping apparatus can be used to wrap any other spherical object in a manner similarly described with respect to the firework shells.

Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a perspective view of an apparatus for wrapping fireworks shells according to the invention;

FIG. 2

is a schematic side view of the apparatus for wrapping fireworks shells;

FIG. 3

is a schematic front end view of a portion of the apparatus for wrapping fireworks shells;

FIGS. 4-7

illustrate the initial assembly of a spherical firework shell according to the invention;

FIG. 8

illustrates using a device to locate a fuse marker; and

FIG. 9

is a schematic illustration showing an adjustable embodiment of the apparatus for wrapping fireworks shells adapted to wrap spherical shells of various diameters.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to

FIGS. 1 through 3

, an apparatus for-wrapping fireworks shells

10

generally includes a base

12

provided with preferably three support rollers

14

,

16

,

18

configured to support a spherical firework shell

20

of a predetermined size thereon, stepper motors

22

,

24

coupled to two of the rollers

14

,

16

, and a computer

26

electrically communicating with the stepper motors

22

,

24

to control the movement of the stepper motors and thereby control the angular rotation of the shell

20

on the rollers

14

,

16

,

18

. Also included are a dispenser

28

which stores and feeds a continuous roll of tape

30

for wrapping the shell, spools

32

,

34

,

36

,

38

for guiding the tape

30

from the dispenser to the shell, and a pressure applicator

40

that presses the tape to the shell

20

as the shell is rotated on the rollers. Preferred tape include one to two inch, 40 to 60 lb tape.

More particularly, the base

12

includes a frame

50

and legs

52

which support the frame. The stepper motors

22

,

24

are preferably rigidly coupled to the frame

50

and include rollers

14

,

16

, respectively at the ends thereof. Support roller

18

is also coupled to the frame

50

such that the support rollers

14

,

16

,

18

are in a triangular arrangement, and adapted to stably support the spherical shell

20

. The support rollers are preferably made from 30 durometer silicon rubber

6

r another preferably elastomeric material that provides the necessary traction to cause the shell.

20

to rotate when the support rollers are rotated. Additionally, one or more of the rollers may be embedded with exposed metal studs to increase traction. Other means for traction, i.e., an elastomeric or non-elastomeric roller material provided with a high friction surface coating or exposed material or elements, may be used.

The dispenser

28

is adapted to hold a relatively large roll of tape

30

. The tape

30

includes a preferably water-activated adhesive, and the dispenser includes means (not shown) for applying water to the adhesive side of the tape. Such means may include a bath through which the tape is pulled or a wet sponge or rolling element against which the tape is contacted as the tape is pulled from the tape roll.

The tape

30

extends from the dispenser

28

and across spools

32

and

34

, which are located to guide the tape under the frame

50

. The tape then extends up to spool

36

which guides the tape to spool

38

(over a shell resting on the rollers). The adhesive side of the tape is oriented outward such that it is not in contact with any of the spools. Spool

38

is configured to then guide the tape

30

, adhesive side down, onto a shell

20

located on the rollers

14

,

16

,

18

.

Spool

38

is mounted via a mount

53

on a bar

54

. The bar

54

is slidable along posts

56

,

58

which extend generally upward from the frame

50

. The posts are angled at an elevation angle of at least 45°, and preferably at an elevation angle between 70° and 90°. The pressure applicator

40

includes a contact element

60

also on the mount

53

which directly presses tape

30

from the spool

38

onto the shell

20

, and springs

62

coupled to both the frame

50

and the bar

54

which urge the contact element

60

against a shell

20

located on the rollers. The contact element

60

is preferably a metal coil (e.g., a stiff metal spring) which is generally horizontally oriented at a lower portion of the mount

53

such that the windings of the coil press the tape

30

into the shell

20

. Containment rollers

64

,

66

are provided at a lower portion of mount

53

about the contact element

60

and operate to contain a spherical shell spinning on the support rollers, but preferably do not support any weight of the shell.

The space between the rollers and the extent to which the bar

54

, and therefore spool

38

and contact element

60

, can move up on the posts

56

,

58

is preferably optimized for a particular shell diameter. As such, different shell diameters may require the use of specifically configured apparatus. Table 1 provides approximate presently preferred spacings between the support rollers

14

,

16

,

18

for different size shells.

TABLE 1

Support Roller Spacing

Space between

Space between support roller 18

center of support

and a line extending between the

Shell Size

rollers 14 and 16

center of rollers 14 and 16

 4 inch

  3 inch

3.25 inch

 5 inch

3.25 inch

 3.5 inch

 6 inch

3.75 inch

  4 inch

 8 inch

4.25 inch

 4.5 inch

10 inch

  5 inch

5.75 inch

12 inch

 5.5 inch

6.25 inch

The computer

26

controls the amount (i.e., speed) of rotation of the stepper motors

22

,

24

. The computer

26

may be physically located on the frame

50

(as shown), or may be separately located from the frame, for example, as a personal computer (not shown) coupled to an interface (not shown) which is coupled to the stepper motors. The computer

26

includes a memory that stores one or more programs for operation of the stepper motors (preferably in computer numerical code or ‘CNC’) and a processor which instructs the stepper motors to rotate in accord with a program loaded from the memory. The programs are adapted to individually control the amount of rotation of the motors. By individually controlling the amount of rotation of the stepper motors, and consequently the support rollers attached thereto, the shell is made to rotate in a desired manner such that, at times, the shell is subject to angular rotation. Controlling the rotation of the shell permits the tape to be applied to the shell in a manner which completely covers the shell.

For example, when both support rollers

14

,

16

are rotated by the same amount, the shell is rotated about a first axis aligned with support roller

18

. When the computer

26

causes the stepper motors

22

,

24

to rotate the support rollers

14

,

16

by relatively different amounts, the shell

20

then rotates about other axes. According to a preferred tape wrapping pattern, the stepper motors are controlled to rotate the shell in a ‘figure

8

’ pattern: the shell is rotated about the first axis for a distance of preferably approximately forty percent of the shell circumference, the rotation is then skewed (by offsetting the relative rotational speeds of the stepper motors

14

,

16

) to the left (or the right) for preferably approximately ten percent of the shell circumference, the shell is again rotated about the first axis for a distance of preferably approximately forty percent of the shell circumference, and then the rotation is skewed back to the right (or the left) for preferably approximately ten percent of the shell circumference. As such, after each 360° rotation of the shell, the location being contacted with tape is offset relative to the location of the tape prior to that revolution of the shell. The order of the axial and skewed-rotations, providing straight and curved paths for the tape on the shell, may be altered.

By way of one example, and not by limitation, the following algorithm for controlling the stepper motors is provided and has been shown to provide excellent tape coverage:

rotate skewed left for 0.1 times circumference of the shell

rotate straight for 0.4 times circumference of the shell

rotate skewed right for 0.1 times circumference of the shell

rotate straight for 0.4 times circumference of the shell

repeat ten times

provide offset in rotational speed to prevent tape from directly overlying underlayer

rotate skewed left for 0.1 times circumference of the shell

rotate straight for 0.4 times circumference of the shell

rotate skewed right for 0.4 times circumference of the shell

rotate skewed right for 0.1 times circumference of the shell

rotate straight for 0.4 times circumference of the shell

repeat five times

provide location offset to initiate taping from a different physical location on the shell

go to beginning and repeat until sufficient tape thickness

One skilled in the art of computer numerical code (CNC) and its control of stepper motors will be able to design the necessary CNC for the desired rotation of the shell. The particular CNC will be based upon the shell size, the support roller diameter, the relative angle between the support rollers, the width of the tape, and the thickness of the tape.

In a less preferred algorithm for tape application, the stepper motors may be operated to allow complete rotation of the shell prior to temporarily offsetting the motor speeds, then allowing another complete rotation, and then temporarily offsetting the speeds, etc. As yet another alternative, the support rollers

14

,

16

may always be rotated at relatively different speeds such that the tape is always applied obliquely relatively to an axis of rotation.

In operation, initially, two paper shell half portions (hemishells)

70

,

72

(FIG.

4

), each provided with bursting charge.

74

and stars

76

, are assembled into a spherical shell

20

(FIG.

5

). A single piece of tape

78

(

FIG. 6

) is manually applied to the shell to temporarily maintain the integrity of the sphere. Thus far, the assembly is performed in the conventional manner with one exception. No fuse is provided in the sphere. Rather, referring to

FIG. 6

, according to preferred aspect of the invention, a tube

80

is provided in a fuse hole

81

(

FIG. 5

) flush or recessed with the outer surface of the shell. A marker such as a small magnet

82

is then fixed, for example, with a piece of tape

84

over the end of the tube.

Then, referring back to

FIG. 1

, according to the invention, the spherical shell

20

is provided on the rollers

14

,

16

,

18

, and tape

30

from the dispenser

28

is contacted with a portion of the sphere and pressed thereto by the contact element

60

of the pressure applicator

40

such that it adheres to the shell. The stepper motors

22

,

24

are activated by the computer to rotate the support rollers

14

,

16

, and consequently the shell about a first axis. The containment rollers

64

,

66

stabilize the shell on the support rollers during shell rotation. The tape is applied according to one of the algorithms discussed above, with the tape strip on the shell having a length many times (preferably at least ten and potentially hundreds of times) the diameter of the shell. The shell is wrapped until a sufficient thickness of tape is present to form the desired casing.

Referring to

FIG. 8

, after the shell

20

is wrapped, it is substantially spherical without substantial surface aberration. This is the result of the manner of wrapping and the usage of a relatively flat marker. A suitable element is then used to locate the marker for the fuse. For example, if the marker is a magnet, iron filings can be placed on the shell to locate the markers. The casing is then carefully cut at the marker location with a plug cutter to expose the marker

82

and tube

80

in the fuse hole. After the marker is removed, a fuse

88

is fed through the tube

80

into casing. An epoxy or other sealant is, then applied about the fuse

88

to provide a seal and complete the firework shell.

With the apparatus

10

of the invention, the time for wrapping fireworks shells is greatly reduced, from days to hours, or from hours to minutes, depending on the size of the shell. Moreover, once started, the apparatus

10

can run substantially unassisted and therefore provides a much safer method of manufacture than the completely handmade method.

Turning now to

FIG. 9

, an embodiment of an adjustable firework shell wrapping apparatus

110

able to accommodate shells of various sizes is shown. The adjustable apparatus

110

is substantially similar to the previously described embodiment with the following differences. First, support roller

118

can be moved relative to support rollers

114

and

116

between positions

118

a

,

118

b

,

118

c

, and

118

d

(and intermediate positions therebetween) to stably accommodate spherical shells of various sizes, e.g., 3 inches to 16 inches, and can be designed to accommodate even up to 24 or 36 inch shells. The adjustment may be effected by providing roller

118

on a bearing and having the bearing be slidably disposed along a rod. The bearing may then be slid along the rod and locked at a desired location. Other suitable mechanisms known in the mechanical arts for adjusting one element relative to another may also be used. Second, optionally, the space between support rollers

114

and

116

is adjustable. This adjustment may be affected by having the stepper motors be mounted to the frame in a manner which permits adjustment of the stepper motors relative to the frame. Third, the posts

156

are relatively long such that bar

154

can be set on the posts in a position which permits the spool

138

and contact element

160

to suitably guide and press the tape

130

to the shell, and containment rollers

164

,

166

to contain the shell. Fourth, particularly useful for wrapping larger shells, a containment bearing assembly

168

, e.g., comprising three bearings in a triangular arrangement, may be provided to further stabilize a shell on the support rollers. The containment bearing assembly

168

is preferably spring-loaded against a shell, and may be adjusted for different size shells. As such, the wrapping apparatus

110

is capable of accommodating shells of various sizes.

There have been described-and illustrated herein embodiments of an apparatus for wrapping fireworks shells, a method of wrapping firework shells, and a firework shell produced by the method. While particular embodiments of the invention have been described, it is not intended that the invention be limited thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. Thus, while a water-activated tape is disclosed for wrapping the shells, it will be appreciated that other tapes or wrapping materials can be used as well. For example, kraft paper drawn through a paste bath may be applied to the shells. In addition, while a preferred stepper motor program has been disclosed, it will be understood that other programs can likewise be used. Also, while the apparatus has been described with three rollers, it will be appreciated that additional rollers can be used to further support the shell. Furthermore, while spools are described for guiding the tape, it will be appreciated that guides of other shapes and design may be used as well. Moreover, while a metal coil has been described for applying pressure to press and/or burnish the tape to the shell, it will be appreciated that contact members of other design may be used as well. Also, while roller

18

(

118

) is preferably free-spinning, it may also be coupled to a motor for active rotation. In addition, while a magnetic marker is disclosed, the marker may be another metal or another material otherwise discernable, such as by x-ray or MRI. Furthermore, one or more markers may be used to point to or otherwise identify the fuse hole, rather than be provided above the fuse hole. Moreover, water or paste can be applied either right at or before the contact element, or could be applied to the shell directly near the point of contact with the tape. Also, while several tape patterns have been disclosed, it will be appreciated that yet other patterns may be used in the application of the tape to the shell. Further, as an alternative to the springs

62

, pneumatic cylinders may be used. Also, while a computer with a processor and memory have been disclosed, it will be appreciated that dedicated circuitry and sensors, or any other hardware and/or software combination can be to control the stepper motors. In addition, while the embodiment of the wrapping apparatus have been described with respect to wrapping a spherical firework shell, it is recognized that the apparatus can be used to tape or wrap any spherical object sized to be positioned on the rollers. It will therefore be appreciated by those skilled in the art that yet other modifications could be made to the provided invention without deviating from its spirit and scope as claimed.