Expansion ring and clip for use with an expandable oven

An expansion ring for expanding the size of an oven is disclosed. The expansion ring has a plurality of expansion ring segments which are connected together by one or more clips. The expansion ring segments have end portions which, when two segments are placed in end-to-end relation, form an engagement portion having first and second stops. The clip has a channel which engages the engagement portion so as to hold the expansion ring segments together and a finger projecting into the channel. According to this arrangement, the clip is slidable between a first position where the finger engages the first stop and a second position where the finger engages the second stop. In the first position, the expansion ring segments are locked together. In the second position, the segments may be separated, but the clip remains attached to one of the segments so that it will not be lost. An oven incorporating the expansion rings and clips of the present invention is also disclosed.

BACKGROUND OF THE INVENTION 
The present invention relates generally to a multi-piece expansion ring 
used to expand the size of a portable oven, and to a unique clip used to 
hold the pieces of the expansion ring together. More specifically, the 
present invention relates to such an expansion ring/clip combination which 
securely holds the expansion ring segments together, but allows for easy 
disassembly of the expansion ring for cleaning and storage. 
The concept of using expansion rings to increase the cooking capacity of a 
portable oven is disclosed in U.S. application Ser. No. 325,157 filed Mar. 
17, 1989 and assigned to the same assignee as the present invention. The 
present invention it is particularly useful with the oven disclosed in 
Ser. No. 325,157. To the extent that the disclosure of that application is 
necessary to an understanding of the present invention, it is incorporated 
by reference herein. 
It is desirable for a number of reasons to form an expansion ring out of 
two or more segments. Such a multi-segment design is easier to 
manufacture. It is also more compact for shipping and storage purposes, 
and is easier for the user to clean. 
When such a multi-piece extension ring is used, some means must be provided 
to connect the segments together. One such means which is known is the 
clip shown in FIG. 1. This clip, which is made of aluminum, has a 
generally planar front face 2 and a rounded back face 4. A slot 6 is 
formed along the front face of the clip. The expansion ring segments (not 
shown) have projections extending along the free ends thereof. The 
projections are shaped so that when two expansion ring segments are placed 
together, the projections of the two segments together form a shape 
generally the same as that of slot 6. Thus, the clip can be slid over the 
two projections so as to hold the segments together. 
The clip of FIG. 1 suffers from numerous disadvantages. Several 
disadvantages result from the use of aluminum for the clip. One, aluminum 
has high thermal conductivity. Thus, when the oven is heated up, the clips 
tend to heat up quickly and retain that heat. These hot clips are 
potentially dangerous to the user, who can be burned. 
Two, the expansion ring segments are made of plastic, which has a different 
thermal expansion rate than the aluminum of the clips. Thus, when the oven 
is used, the plastic expansion ring segments expand faster than the clips. 
This causes great stress to be placed on the projections, which can crack 
under the pressure. 
Another related problem is that the only thing holding the clip in place is 
friction. If the clip is designed to fit tightly on the projections so as 
to remain securely in place, then the cracking problem referred to in the 
previous paragraph is particularly troublesome. One the other hand, if the 
clip is designed to only loosely fit over the projections, the clip is not 
held securely, and has a tendency to fall off. 
One solution which has been suggested is shown in FIG. 2. The only 
difference between the clip of FIG. 2 and that of FIG. 1 is the use of two 
small bumps 8 located within space 6. The bumps are designed to cooperate 
with two small detents located on the projections of the expansion ring 
segments. 
However, this clip, which is also made of aluminum, still suffers from 
disadvantages. Importantly, when the clip is slid on and off numerous 
times, the metal bumps on the clip eventually form a groove in the softer 
plastic of the expansion ring segments. This loosens the fit of the clip 
on the projections, so that eventually the bumps and detents would cease 
to served any function. 
Finally, the aluminum clips shown in FIGS. 1 and 2 are very labor 
intensive, and thus expensive, to produce. 
SUMMARY OF THE INVENTION 
The present invention includes an expansion ring having a plurality of 
expansion ring segments connected together by at least one clip. The 
expansion ring segments have end portions which, when two segments are 
placed in end-to-end relation, form an engagement portion having a first 
stop. The clip is designed to engage the engagement portion so as to hold 
the expansion ring segments together. A finger is formed on the clip which 
engages the first stop so as to hold the clip in the engaged position. 
The clip preferably has a channel portion which forms a channel extending 
along the length of the clip. The channel portion is C-shaped in 
longitudinal cross-section. The engagement portion is shaped so as to fit 
within the channel. Thus, when two expansion ring segments are fit 
together, the clip can be slid over the engagement portion so as to lock 
the segments together. 
The engagement portion preferably has a second stop, and a sliding surface 
located between the first and second stops. According to this arrangement, 
the clip is slidable between a first position where the finger engages the 
first stop and a second position where the finger engages the second stop. 
In the first position, the expansion ring segments are locked together. In 
the second position, the segments may be separated, but the clip remains 
attached to one of the segments so that it will not be lost. In between 
the first and second positions, the finger presses against the sliding 
surface, providing a frictional resistance which results in smooth 
movement between the two positions. 
The clip is preferably made of plastic. Such a plastic clip is easy and 
inexpensive to manufacture. It is also less damaging to the expansion ring 
segments, which are also made of plastic. The plastic has a low thermal 
conductivity, so it is less likely that the user will be burned during use 
of the oven. Finally, because the finger of the clip is plastic, it can be 
easily deformed by the user so as to disengage the finger from the first 
and second stops. 
The invention also includes an oven which employs such an expansion ring 
and clips.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An oven employing an embodiment of the expansion ring of the present 
invention is shown in FIG. 3. This oven is disclosed in Ser. No. 325,157, 
which is incorporated herein by reference. 
As shown in FIG. 3, the oven preferably has an upper enclosure member 11 
and a lower enclosure member 13 which define a cooking chamber. The 
cooking chamber is generally circular in horizontal cross-section and 
ovular in vertical cross-section. A rack (not shown) is provided within 
the lower enclosure member for supporting the food to be cooked. A housing 
17 is fitted in an opening in the upper enclosure member. The housing 
contains a heating element (not shown) and a fan blade/motor assembly (not 
shown). As explained in further detail in Ser. No. 325,157, the heating 
fan blade moves the air at a high velocity within the cooking chamber, 
causing the food to be quickly and evenly cooked. 
The oven preferably includes an interconnecting member 19 which connects 
the upper and lower enclosure members together. The interconnecting member 
is made up of an upper support portion 21 and a lower support portion 23. 
Upper support portion 21 has a horizontal leg 21a, which is connected to 
housing 17, and a vertical leg 21b. Likewise, the lower support portion 
has a horizontal leg 23a and a vertical leg 23b. The horizontal leg rests 
on the supporting counter top or table, and can connect to one of the feet 
of the oven. The vertical legs 21b and 23b cooperate as a hinge to allow 
the upper enclosure member to pivoted upwardly to allow access to the 
interior of the oven. 
In order to expand the size of the cooking chambers, an expansion ring such 
as 25 is placed between the upper and lower closure members. An expansion 
spacer 27 is placed between upper and lower support portions 21 and 23 so 
as to increase the height of the interconnecting member as well. 
Expansion ring 25 is shown in greater detail in FIG. 4. The expansion ring 
is preferably made up of two expansion ring segments 28 and two clips 31. 
The expansion ring segments are preferably identical, each being generally 
semi-circular in horizontal cross-section. Located along one edge of the 
expansion ring segments is a stepped portion 38. This stepped portion is 
designed so that the upper enclosure member rests on the stepped portion, 
so as to hold the upper enclosure member securely and stably on the 
expansion ring. 
Each expansion ring segment has a first end portion 34 and a second end 
portion 36 (only one end portion of each expansion ring segment is shown 
in FIG. 4). The first and second end portions are planar on both their 
inner and outer faces. First end portion 34 has a lug 39 on the outer flat 
face thereof and a projection 31 projecting from the edge surface. Lug 39 
has a stepped portion 40 (see FIG. 9). Second end portion 36 has a lug 42 
which is substantially identical to the lug 39 on the first end portion. 
Lug 42 also has a stepped portion 43 (FIG. 9). Formed integrally with lug 
42 on the second end portion is a second lug 44. Lug 44 is wider than lugs 
39 and 42 and is flat on its outer surface. A notch 41 is located behind 
the second lug. 
Clip 31 has a rounded outer surface 45 and a substantially planar inner 
surface 47. A channel 48 extends along the length of the clip. The channel 
is substantially C-shaped in cross-section. A notch 50 is located in the 
outer surface of the clip at one end thereof. Within the notch is a 
substantially L-shaped finger 52. One leg 53 of the L-shaped finger 
extends generally in parallel to the outer surface 45 of the clip and 
projects just past the outer surface. The other leg 54 of the L-shaped 
finger projects just past the end of channel 48 (see FIGS. 6 and 7). 
The end portions 34 and 36 of the expansion ring segments are designed to 
mate together as shown in FIG. 5. In the mated position, projection 41 of 
the first end portion fits within notch 44 of the second end portion (see 
FIG. 8). Furthermore, lugs 39, 42 and 44 cooperate to form an engagement 
portion 56. The engagement portion is shaped to fit securely within 
channel 48 of the clip. A first stop 58 is formed by the ends of lugs 39 
and 42 A sliding surface 60 is formed by the two stepped portions 40 and 
43. A second stop 62 is formed at the junction between the sliding surface 
and second lug 44. 
The manner in which clip 31 cooperates with the engagement portion 56 will 
be described with reference to FIGS. 6-7. So that the interaction of the 
clip and the engagement portion can be seen clearly, only one of the 
expansion ring segments is shown in FIGS. 6-7. However, it is understood 
that the clip is designed to engage two expansion ring segments mated 
together as shown in FIG. 5. 
The clip is shown in the unsecured position in FIG. 6. In this position, 
lug 44 is securely held with the channel of the clip. Finger 52 engages 
stop 62 so as to prevent the clip from sliding up. In this position, the 
expansion ring segments are not connected together, since the channel of 
clip 31 has engaged only lug 44, and not lugs 39 and 42. However, because 
stop 62 prevents the clip from sliding upwardly, the clip remains attached 
to one of the expansion ring segments, thus reducing the chance that the 
clip will be lost during shipping, storage, cleaning, etc. If it is 
necessary to completely removed the clip from the expansion ring segment, 
finger 52 can be bent back manually, thus disengaging the finger from stop 
62. Once disengaged, the clip can be slid up and off of the engagement 
portion. 
To secure the two expansion ring segments together, the clip is slid down 
over the two lugs 39 and 42. As the clip is slid downwardly, lugs 39 and 
42 and engaged by the channel 48. Furthermore, finger 52 presses against 
sliding surface 60 so as to provide smooth movement between the secured 
and unsecured positions. 
The clip is shown in the secured position in FIG. 7. In this position, 
finger 52 is located past the end of the engagement portion 56 so as to 
engage the first stop 58. Once engaged with the first stop, the clip is 
locked onto the engagement portion, and will not slide off accidentally. 
The channel grips the two lugs 39 and 42 together so as to securely hold 
the expansion ring segments together. Ledge 64 located along the lower 
edge of end portions 34 and 36 prevent the clip from sliding downwardly. 
To disconnect the expansion ring segments, one simply lifts up on finger 52 
and slides the clip back to the position shown in FIG. 6. 
The expansion ring segments are made out of a high temperature plastic, 
preferably PAS (Poly Aryl Sulfone). The clips are also made out of 
plastic, preferably of a material sold by DuPont under the name Zytel. The 
clips can be made cheaply and easily by, for example, injection molding. 
The plastic material ensures that the finger 52 is easily bendable, 
allowing the finger to be manually lifted out of engagement with the stops 
on the engagement portion. The plastic clips are also preferable because 
their low thermal conductivity allows the clips to stay cool during use of 
the oven. Also because the clips and expansion ring segments are made out 
of material with similar thermal expansion rates, the channel can be sized 
to fit snugly on the engagement portion, without fear that the engagement 
portion will bind or crack when the oven is heated up. 
The foregoing constitutes a detailed description of the preferred 
embodiment of the oven, expansion ring, and clips of the present 
invention. However, the invention is not limited to the preferred 
embodiment. Numerous changes are possible without departing from the 
spirit and scope of the invention. For example, the oven and expansion 
rings need not be circular, but can be of any desirable shape. More than 
two expansion ring segments may be used. The size, shape, and arrangement 
of many parts may be changed. Thus, the scope of the invention should be 
defined with reference not to the preferred embodiment, but to the 
following claims.