Bellows with flexible stem for saw

Scroll saws produce an accumulation of sawdust or other debris removed from a workpiece during operation of the saw. This debris can block the operator's view of the cutting path of the saw. An improved device and method for removing accumulated debris from the cutting path of a saw blade is disclosed. A bellows is described, comprising a bellows section having an accordion-like structure and a flexible stem having a passage through which air may pass. The bellows may be manufactured as a single piece using a blow molding process to achieve greater structural integrity. A scroll saw having a bellows for removing debris and a protective cover for use with the bellows is also described.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to bellows for removing debris from 
the cutting path of a saw and, more particularly, to a bellows with a 
flexible stem for use in a scroll saw. 
2. Description of the Related Art 
Scroll saws (or jig saws) typically comprise a saw blade connected between 
the free ends of two reciprocating arms. A frame supports the 
reciprocating arms and a work table positioned so that the saw blade 
passes through an opening in the work table. The reciprocating arms are 
attached to the frame by bearings that permit the arms to pivot, and a 
motor is linked to the reciprocating arms. In operation, the motor causes 
the arms to rapidly reciprocate about their pivots, causing the saw blade 
to move up and down rapidly. A scroll saw of this type is described in 
U.S. Pat. No. 5,197,369, which is hereby incorporated by reference. 
During operation of the scroll saw, a workpiece is cut by placing the 
workpiece against the reciprocating saw blade and guiding the workpiece so 
that a cut of the desired shape is made. However, sawdust, metal filings, 
or other material removed from the workpiece by the saw blade can 
accumulate on the workpiece and hinder efficient operation of the scroll 
saw by blocking the operator's view, thereby preventing the user from 
accurately controlling the shape of the cut. The present invention 
provides an improved device and method for removing accumulated sawdust or 
other debris from the cutting path of a saw blade. 
Bellows have been used in the past in scroll saws to blow air to remove 
sawdust from the cutting path of the saw blade. Bellows are suited for 
this application because the reciprocating movement of the scroll saw's 
arms can be conveniently used to repeatedly compress and release the 
bellows, generating the desired airflow. 
Previous bellows designs have included a short, non-flexible nipple at one 
end of the bellows for connection to a flexible air hose that is used to 
direct the airflow in the desired direction. However, when such bellows 
are used in applications with space restrictions requiring the air hose to 
make a right-angle bend near to its point of attachment to the bellows, 
the vibration of the scroll saw tends to cause the air hose to work loose 
from the nipple. To solve this problem, some designs have included a 
separate rigid elbow-shaped tube with a right-angle bend that connects to 
the nipple on the bellows at one end and the air hose at the other end. 
This design requires the elbow to be manufactured as a separate piece from 
the bellows because the blow molding process typically used to make the 
bellows cannot be used to produce an angled nipple. 
Another problem occurs when a blow molding process is used to produce the 
bellows from a plastic material. Although this method of manufacture is 
very economical, it often produces wall thickness irregularities in the 
article being manufactured. These irregularities occur in the area where 
the blow vent needle is located. Any irregularity in the wall thickness 
will create internal stresses in the plastic material when the area with 
the irregularity is flexed, leading to cracking of the wall. During 
operation of the bellows, the bellows section is repeatedly compressed and 
released, flexing the walls of the bellows section. Thus, any wall 
thickness irregularities in the bellows section increases the risk of 
premature failure of the part. 
SUMMARY OF THE INVENTION 
The present invention addresses the problems described above by providing a 
bellows with a bellows section having an accordion-like structure, and a 
flexible stem having a passage through which air may pass. The flexible 
stem permits the connection between the bellows and the air hose to be 
made without placing stress on the connection point. In situations 
requiring the air to be directed at right-angles to the axis of the 
bellows, the flexible stem can be made to bend and the air hose made to 
follow a straight path. As a result, the connection between the nipple at 
the end of the flexible stem and the air hose is subject to less stress 
and is less likely to become disconnected during operation. Corrugations 
in the flexible stem permit the stem to bend without collapsing and 
restricting the flow of air through the stem. 
In accordance with another aspect of the invention, a bellows is provided 
having a bellows section and a flexible stem manufactured as a single 
piece. The one piece construction permits the blow vent needle to be 
located at the nipple end of the flexible stem, away from the bellows 
section. Any wall thickness irregularities around the blow vent needle 
will thus be located at the nipple end of the flexible stem, where the 
stresses on the wall are at a minimum. 
A scroll saw having a bellows for removing debris from the cutting path of 
the saw constitutes another aspect of the invention, where the bellows 
comprises a bellows section having an accordion-like structure, and a 
flexible stem having a passage through which air may pass. A method of 
removing debris from the cutting path of a saw is a further aspect of the 
invention. The method comprises providing a bellows comprising a bellows 
section and a flexible stem, compressing the bellows section of the 
bellows, and directing the air expelled by the bellows onto the cutting 
path of the saw.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
1. PHYSICAL CONSTRUCTION 
Turning now to the drawings and referring initially to FIG. 1, a 
perspective view is given showing a preferred embodiment of a one-piece 
bellows 10. A bellows section 12 comprises two surfaces, a first surface 
14a and a second surface 14b, connected by an accordion-like structure. 
The bellows section 12 is capable of contraction and expansion as the 
first surface 14a and second surface 14b are pressed together or allowed 
to move apart. The bellows section 12 is elongated with rounded ends, 
although a circular, square, rectangular or other shape may be used as the 
particular application requires. 
A flexible stem 16 extends from the first surface 14a of the bellows 
section 12. The flexible stem 16 has several corrugations 18a, 18b, 18c 
and 18d, formed by alternately increasing and decreasing the diameter of 
the flexible stem 16 along its length, as shown in FIG. 1. The 
corrugations permit the stem to bend without collapsing and restricting 
the flow of air through the stem. The flexible stem 16 has a nipple 20 at 
its is end to permit connection to an air hose. A hub 22 comprising a 
raised area protrudes from the second surface 14b of the bellows section 
12, opposite to the flexible stem 16. The hub 22 provides a convenient 
means to secure a protective cover to the bellows. 
FIG. 2 shows a cross-sectional view of the embodiment shown in FIG. 1. The 
bellows section 12 creates an enclosure having a variable volume, and the 
flexible stem 16 has an internal passage through which air is drawn into 
and expelled from the bellows section 12. The walls of the bellows section 
12 are essentially of uniform thickness. Although the bellows is 
illustrated with the flexible stem facing downwards, the bellows may be 
effectively used in any orientation. 
FIG. 3 shows a cross-sectional view of a portion of a scroll saw showing an 
embodiment of the invention installed in the scroll saw. A frame member 30 
provides support for a reciprocating arm 32. Only a portion of the upper 
section of the frame and the upper reciprocating arm are shown in the 
drawing. The upper reciprocating arm 32 pivots about bearing 34, causing 
the saw blade (not shown) to move up and down. The bellows is positioned 
between the stationary frame member 30 and the upper reciprocating arm 32 
so that the bellows section 12 of the bellows is alternately compressed 
and released as the reciprocating arm 32 pivots about bearing 34. The 
flexible stem 16 extends through a portion of the reciprocating arm 32, 
keeping the bellows in place. An air hose 36 connects to the nipple 20 of 
the bellows. The air hose 36 is routed through the reciprocating arm 32 
and its open end is positioned to direct the air expelled from the bellows 
onto the cutting path of the saw. 
FIG. 4 shows a preferred embodiment of a bellows protective cover. A 
separate rigid bellows protective cover 38 may be used to protect the 
bellows from physical damage that may result from rubbing or pressing on 
sharp areas of the reciprocating arm or scroll saw frame. A preferred 
embodiment of the bellows cover 38 includes fingers 40a and 40b shaped to 
engage the hub protruding from the bellows section. Sides 42a and 42b 
provide additional protection for the bellows. 
FIG. 5 shows a scroll saw arm with a bellows and a protective cover. The 
protective cover 38 fits over the bellows section 12 as shown in the 
drawing. 
2. THE MANUFACTURING PROCESS 
The bellows may be conveniently and economically manufactured from a 
thermoplastic material using an extrusion blow molding process. A 
preferred material is low density polyethylene, although other materials 
may also be suitable. In the extrusion blow molding process, a 
heat-softened thermoplastic tube is extruded in the approximate shape of 
the article being manufactured. One end of the tube is pinched to close 
the end and the other end is sealed around a blow vent needle (or blow 
pin), producing a partially inflated balloon of thermoplastic material. 
The two halves of a female mold are closed around the balloon of material 
and air is blown through the blow vent needle, forcing the balloon to 
expand and take the shape of the internal cavity of the mold. The blow 
vent needle is then removed and the mold opened, ejecting the part. When 
the blow vent needle is removed from the mold, plastic material often 
adheres to the blow vent needle resulting in a thick walled section in the 
article being blow molded at the point where the blow vent needle is 
located. 
In the manufacture of the bellows, the blow vent needle used in the blow 
molding process is preferably located at the nipple 20 on the end of the 
flexible stem 16. This location is chosen because any irregularities in 
the wall thickness of the blow molded bellows that are caused by the 
removal of the blow vent needle will be at a point away from the bellows 
section 12 of the bellows. Wall thickness irregularities in the bellows 
section will often lead to premature failure of the bellows, due to the 
repeated flexing of the bellows section walls during operation of the 
bellows. Any such irregularities at the nipple 20 of the flexible stem 16 
will not cause this problem. 
After removing the bellows from the mold, excess plastic material is 
removed the outer surface of the bellows. A small hole is drilled along 
the center of the flexible stem 16 to remove any irregularities from the 
inside of the flexible stem and ensure that an open air passage exists 
from the bellows section 12 through the flexible stem 16 to the nipple 20. 
The protective cover 38 may be made from a thin plastic sheet formed by a 
stamping process. The sides 42 may be formed by bending portions of the 
sheet at right angles to the base. Fingers 40 may be formed by cutting a 
circular hole in the base, and making cuts in the base to define two 
fingers of material, one on each side of the hole. These fingers are bent 
upwards at about 45 degrees to the base, forming fingers that engage the 
hub 22 on the bellows section 12. The bellows protective cover is 
preferably made from mylar or a similar material. 
Although the bellows and protective cover may be made using the materials 
and techniques described above, many other materials and methods of 
manufacture may also be used to make these parts. 
3. OPERATION OF THE BELLOWS 
In operation, the bellows section 12 of the bellows is alternatively 
compressed and released. When the bellows section 12 is compressed it 
collapses, forcing air out of the bellows section 12 and through the 
flexible stem 16. The air hose 36 connected to the end of the flexible 
stem 16 directs the air onto the cutting path of the saw blade to remove 
debris. When released, the bellows section 12 expands to assume its 
original shape, drawing air back into the bellows section 12 through the 
flexible stem 16. The open end of the air hose 36 is located close to the 
cutting path of the saw blade to provide optimal debris removal (i.e. 
maximum air force) on the downstroke of the reciprocating arm 32, but not 
so close as to draw debris into the air hose on the upstroke of the 
reciprocating arm 32. 
Many modifications and variations may be made in the techniques and 
structures described and illustrated herein without departing from the 
spirit and scope of the present invention. Accordingly, it should be 
understood that the methods and apparatus described herein are 
illustrative only and are not limiting upon the scope of the present 
invention.