Inject-eject system for rack mounted plug-in modules

An injector/ejector system that provides for easy insertion and removal of a printed circuit board module into and out of a mainframe. The injector/ejector system is defined by a unitary lever arm and two curved finger extensions oppositely situated and which is attached to a front panel of a circuit board module proximate to an exterior corner of the circuit board module. The lever is attached with a shoulder screw assembly to the module and operates through a cutout notch in the front panel that extends approximately 4.0 mm from the edge of the front panel. The grasping end of the lever arm is formed in such a manner that when the module is in the installed position, the grasping surface of the lever is approximately 3.7 mm away from the surface of the front panel, thus allowing the operator to insert his/her fingertip between the front panel of the module and the lever, thus permitting actuation of the ejection process by the operator's fingertip. The lever is preferably made of steel to reduce the probability of galling of injection/ejection bearing surfaces on both the lever and the mainframe.

FIELD OF THE INVENTION 
The present invention relates generally to the field of circuit board 
inject/eject systems and more particularly to systems including a printed 
circuit board plug-in unit having an integral front panel, such as VXI 
modules. In particular, this invention provides an improved inject/eject 
lever system for the insertion and ejection of printed circuit boards to a 
circuit board rack, such as a VXI mainframe. 
BACKGROUND OF THE INVENTION 
In the electronics industry, printed circuit boards are often 
interconnected in card cages or mainframes that include mounting hardware 
and electrical connections for receiving the printed circuit boards. A 
typical system is a VXI mainframe and corresponding printed circuit (PC) 
board modules, which have been standardized by the VXI Consortium 
recommendations for interchangeability between different vendors. 
Generally, the printed circuit boards are housed in modules which are 
slidably received by the mainframes with the electrical connection being 
made by electrical plug-in connectors at the back of the printed circuit 
boards and corresponding electrical connections in the mainframe. 
The gripping action provided by the two interconnected electrical 
connectors: namely, the connector or connectors carried by the printed 
circuit board and the connector or connectors associated with the card 
cage or mainframe, make it difficult to insert and remove the printed 
circuit board plug-in module from the electrical connectors of the card 
cage. Typically, two handles are mounted on the front panel of the plug-in 
module to permit the plug-in module to be manually pushed-in and 
pulled-out of the mainframe connectors. This brute force method of 
injection/ejection can damage the mainframe, the module or the electrical 
connectors. It is also a difficult process if the mainframe is not against 
a supporting wall or is on wheels. Moreover, as the number of inputs and 
outputs per PC board increases, the force required to insert and remove 
the modules from the mainframe increases. Currently, plug-in modules can 
have between 96 and 320 electrical connection pins which correspond to an 
injection/ejection force of approximately 24 to 75 pounds. 
Accordingly, ejectors have been mounted on the front panel of some types of 
plug-in modules as an aid in extracting the printed circuit board plug-in 
modules from the electrical connectors of the mainframes. In VXI 
mainframes, a common extruded aluminum surface is conventionally provided 
on the mainframe adjacent to the front panel of the plug-in module to 
function as a fixed ejection surface for any ejector mounted to the front 
panel of the module. 
A typical prior art ejector facilitates the removal of the module by using 
a pivoting lever arm to bear against the fixed ejection surface and reduce 
the force necessary to be applied by the user. Existing ejectors typically 
consist of several components which must be assembled and attached to the 
mainframe or, in some cases, to the printed circuit board. There are 
typically two ejectors on each printed circuit board module, one adjacent 
to each end of the front panel, to permit ejection of the module without 
skewing or twisting the PC board. One such ejector is disclosed in U.S. 
Pat. No. 4,603,375 to Miller et al, which patent is hereby incorporated 
herein by reference for all that it discloses. 
Some ejector systems have been developed in which the ejector lever is also 
capable of injector operation. One type of system for accomplishing both 
injection and ejection involves use of a member which is pivotally mounted 
on the circuit board, and which includes a single finger that extends into 
a receiver such as a notch in the adjacent frame of the mainframe. This 
type of configuration typically creams excessive fatigue problems on that 
single finger, since that single component is stressed in one direction 
upon insertion, and in the other direction upon ejection. 
Another configuration for accomplishing both injection and ejection using 
the same pivotal device comprises a device which is pivotally mounted on a 
circuit board, and which has a receiver or notch located adjacent the 
mainframe chassis. The mainframe chassis includes a single member such as 
a panel edge that fits within the receiver or notch to provide the bearing 
surfaces. Again, fatigue problems are increased in this type of 
configuration, since a single member provides the bearing surfaces used 
for both insertion and ejection. Furthermore, operation of the 
injection/ejection systems described above involves an inherent problem of 
inserting the single finger within the receiver in the first mentioned 
embodiment, or inserting the notch around the single bearing surface in 
the second mentioned embodiment, during insertion of the plug-in module. 
This requires proper alignment of the insertion/ejection handle or use of 
additional components to accomplish the alignment during the insertion 
process. 
In addition to these problems, the above-described injection/ejection 
systems could not be used in conjunction with present VXI printed circuit 
board plug-in module technology (a new industry standard for the 
configuration of mainframes), since the present VXI standard 
specifications dictate use of an insertion bearing surface that is 
provided by an insertion member positioned on the mainframe chassis at a 
location which is separate and removed from the ejection bearing surface. 
A more recent approach to the problem of injection and ejection of printed 
circuit boards into mainframes is shown in FIGS. 1 and 2, which illustrate 
a pair of injector/ejectors 10A and 10B as components of a system 
including printed circuit board plug-in module 12 having a front panel 14 
secured to one end of the plug-in module 12 in an orthogonal relationship. 
Two longitudinally-slotted openings 11A and 11B in the front panel 14 
permit the pivotal movement of injector/ejectors 10A and 10B. Module 12 
has an electrical connector 16 having shrouded male pins 18 extending 
outwardly therefrom, two such electrical connectors 16 are illustrated in 
FIG. 1 that are arranged adjacent opposite corners of module 12 and 
adjacent the inner edge thereof. A mainframe is generally defined by a 
pair of spaced module guides 20 (partially illustrated) of conventional 
construction. Guides 20 are provided with a longitudinal slot to slidably 
receive and guide opposite edges of module 12 in its travel toward the 
rear of the mainframe chassis. The mainframe includes electrical 
connectors 22 that are mounted in a spaced relationship with guides 20 and 
fixed in position between the ends of the guides so as to receive the male 
pins 18 of connectors 16 in electrical circuit relationship. Connectors 22 
are suitably supported by the mainframe (not shown) in a fixed position 
and have female receptacles for receiving the pins 18. 
The configuration of the mainframe chassis includes a common surface 24 
that functions as an ejection bearing surface for extracting the 
electrical connectors 16 from the electrical connectors 22. The ejection 
bearing surface 24 is arranged behind the front panel 14 of the module 
when the four electrical connectors 16 and 22 are interconnected. Ejection 
bearing surface 24 is behind front panel 14 at the top and bottom thereof, 
providing an ejection bearing surface for both injector/ejectors 10A and 
10B. Likewise, an injection bearing surface 26 is also provided on an 
inner surface of the mainframe chassis, adjacent to the forward end of 
plug-in module 12, at both top and bottom. 
Injector/ejectors 10A and 10B function in response to a pivoting force 
applied thereto, which force is transmitted to the ejection bearing 
surface 24 to cause the plug-in module 12 to be moved outwardly from the 
electrical connectors 22 in response thereto. Specifically, with reference 
to FIG. 2, when a downward pivotal force is applied to 1ever 30, ejection 
surface 34 of ejection finger 32 contacts ejection bearing surface 24, 
transmitting the pivotal force and causing connectors 16 of plug-in module 
12 to be disengaged from connectors 22. 
Also extending from the base of lever handle 30 in a downwardly direction 
spaced from ejection finger 32 is an injection finger 36. The lower 
forward portion of injection finger 36 defines a ridge that extends 
generally in the direction of the ejection surface 34, and forms an 
injection surface 38. The injection bearing surface 38 contacts injection 
bearing surface 26, and communicates forces from the lever handle 30 
through the injection finger 36 and injection surface 38 to the injection 
bearing surface 26 during injection of the plug-in module 12 into the 
mainframe chassis. 
The injector/ejector system just described is disclosed in U.S. Pat. No. 
4,996,631 entitled Injector/Ejector System for Rack Mounted Plug-in 
Modules with Front Panels by Freehauf, which patent is hereby incorporated 
by reference for all that it teaches. Freehauf teaches an aluminum lever 
that is made by a machining or metal extrusion process. Since the current 
VXI standard calls for injection and ejection bearing surfaces along the 
front of the mainframe to be aluminum, Freehauf's aluminum levers are 
prone to cause galling of the injection and ejection bearing surfaces of 
the mainframe or the lever. 
Freehauf's system further teaches two elongated apertures in the front 
panel 14 of the plug-in module to accommodate the two injector/ejector 
levers 10A and 10B. The apertures and the levers extend approximately 
7.7-8.0 mm from the panel edge, thus limiting the useful area of the front 
panel to approximately 22.3-22.0 mm. This can be problematic as today's 
plug-in module front panels are often crowded with electrical components, 
including connector pins that are also placed on the front of the P.C. 
board plug-in modules to accommodate the connection of terminal cards, 
inputs and outputs, or other electrical interconnections beyond those 
provided at the back of the mainframe. Thus, the space on the front panel 
is necessary for electrical connectors which now contain upwards of 300 
pins. 
Freehauf's injection/ejection system also requires 6 additional components 
beyond the front panel and the circuit board to be manufactured and 
assembled. This is a costly solution both in the cost of the components 
and the cost of assembly/disassembly. 
Still further, in the module's installed position, the back surface 80 of 
Freehauf's lever 30 is flush with the front panel 14, which requires the 
wedging of the user's fingernail, a screwdriver blade or other flat object 
under lever 30 in order to start the ejection process. As 24-75 pounds of 
force is required to eject the module and Freehauf's system permits only a 
minimal amount of rotation before surface 34 of lever 30 engages surface 
24 of the mainframe at the commencement of the ejection procedure, this 
procedure has resulted in many damaged fingers, fingernails, and front 
panels due to users trying to pry the lever 30 up from the front panel. 
It would, therefore, be a substantial improvement in the technology to 
provide an injector/ejector system adapted for use with VXI (and other) 
printed circuit board plug-in module technologies, and which avoids the 
difficulties of existing systems such as excess force on the P.C. board, 
mainframe, module, or electrical connectors; excess stress on and twisting 
of the P.C. board; excess fatigue and galling of lever fingers or extruded 
injection/ejection force bearing surfaces of the mainframe; excess number 
of inject/eject components; excess usage of front panel space for the 
inject/eject system; or excess damage to user's fingers or the front panel 
due to the user having to pry the inject/eject lever from the surface of 
the front panel at the beginning of the ejection process. 
SUMMARY OF THE INVENTION 
The present invention comprises an improved injector/ejector system in 
which the number of components are reduced over the systems of the prior 
art and the injecting and ejecting operations are effectuated by 
components separately spaced from the lever and made of such material and 
in such a manner to thereby increase the durability of the system and 
reduce the stress, wear, and galling that occurs to the stress bearing 
surfaces of the prior art solutions. The present invention also increases 
the useable panel space and improves the ease of use over the 
injection/ejection system of the prior art. The injector/ejector system of 
the present invention may be utilized in any currently specified VXI 
printed circuit board plug-in module system and other electronic plug-in 
module system. 
In one preferred embodiment, the present invention may comprise an 
injector/ejector defined by a unitary lever arm and two finger extensions 
oppositely situated and which is attached to a front panel of a circuit 
board proximate to an exterior corner of the circuit board. The lever is 
attached with a shoulder screw assembly comprised of a screw, bearing, and 
friction spring to a corner shaped mounting block positioned on the 
opposite side of the circuit board. 
The lever is manufactured of stainless steel and thus will not promote the 
galling of the extruded VXI inject/eject bearing surface which is 
aluminum. Due to the configuration of the inject/eject lever of the 
present invention, the mechanical advantage of the lever is approximately 
4.0 for insertion and 3.0 for ejection. Stated differently, the present 
invention requires 1/4 the necessary force for insertion and 1/3 the 
necessary force for ejection to be supplied by the operator. This is a 
substantial improvement over the prior art. 
The lever handle extends outwardly through a notch in one edge of the front 
panel that is orthogonally secured to the printed circuit board by means 
of a corner mounting block such that the front panel is secured adjacent 
and perpendicular to the exterior vertical edge of the circuit board. The 
upper end of the lever arm is formed in such a manner that when the module 
is in the installed position, the grasping surface of the lever is 
approximately 3.5-4.0 mm away from the surface of the front panel, thus 
allowing actuation of the lever for the ejection process by the operator's 
fingertip, rather than the operator's fingernail. 
The finger that actuates the ejection process operates through an aperture 
in the front panel that is situated proximate to the notched edge and the 
outside corner of the front panel. The ejection finger is also formed in 
such a manner that approximately 17 degrees of rotation is permitted 
before the ejection bearing surface of the mainframe is engaged, thus 
permitting the operator to obtain leverage under the lever before the 
ejection process begins. The extension finger that actuates the injection 
process remains on the interior side of the front panel, its exposure to 
the outside being unnecessary for effective operation. 
These and other features and advantages of the present invention will be 
better understood with reference to the following description and appended 
claims taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, the improved inject/eject system for rack 
mounted printed circuit plug-in modules will be examined in further 
detail. The reference characters without letters represent the the 
invention generally, whereas the reference characters with letters 
represent a specific embodiment of the invention. FIGS. 3-5 illustrate a 
pair of inject/eject levers 110A and 110B as components of a system 
including a printed circuit pug-in module 112 having a front panel 114 
secured to one end of the plug-in module 112 in an orthogonal relationship 
therewith. Two notches 111A and 111B and slots 113A and 113B are provided 
on opposite ends along one side of front panel 114 to permit the pivotal 
movement of inject/eject levers 110A and 110B. 
The relationship of module 112 to the corresponding mainframe (partially 
illustrated by element 120) operates similar to module 12 in FIG. 1. 
Specifically, module 112 is slid along guides (not shown) until it is 
mated with electrical connectors (not shown) at the back of the mainframe 
120. The configuration of mainframe 120 includes a common bearing surface 
124 for extracting the electrical connectors (not shown) of module 112 
from the electrical connectors (not shown) of mainframe 120 and a common 
injection bearing surface 126 for inserting the electrical connectors (not 
shown) of module 112 into the electrical connectors (not shown) of 
mainframe 120. 
For the insertion operation, module 112 is slid along the mainframe guides 
(not shown) until it reaches the position slightly beyond that shown in 
FIG. 4. As the injection surface 138 of finger 136 comes into contact with 
mainframe injection bearing surface 126, the operator applies a pivotally 
downward force on lever arm 130A toward the front panel 114 and 
simultaneously applies a pivotally upward force on lever arm 130B toward 
the front panel 114 until the electrical connectors (not shown) of the 
module 112 are engaged with the electrical connectors (not shown) of the 
mainframe 120 and the inject/eject levers 110A and 110B reach the 
configuration as shown in FIG. 3. 
For the ejection operation, the operator inserts his/her fingers under the 
grasping surface 180A of lever arm 130A and the grasping surface 180B of 
lever arm 130B (the levers 110A and 110B are in the configuration as shown 
in FIG. 3). The lever of the present invention has an angled surface at 
the end of the lever arm 130 (FIGS. 7-11) in order to enable the operator 
to slide his/her fingertip under the lever without having to pry the lever 
up with his/her fingernail or some other substantially flat object, such 
as a screw driver blade, which can damage the front panel. The operator 
then simultaneously applies a pivotally upward force to surface 180A of 
lever arm 130A and a pivotally downward force to surface 180B of lever arm 
130B, which causes ejector finger surfaces 134A and 134B to contact 
ejection bearing surfaces 124A and 124B of mainframe 120, respectively. 
The operator continues to apply force until the electrical connectors (not 
shown) of module 112 are disengaged from the electrical connectors (not 
shown) of mainframe 120. Module 112 is slid along the guides (not shown) 
of mainframe 120 and removed therefrom. 
In a preferred embodiment, the ejection finger surfaces 134A and 134B are a 
slight distance from the ejection bearing surfaces 124A and 124B, 
respectively, in order to permit approximately 17.degree. of pivotal 
movement before the ejection bearing surfaces 124A and 124B are engaged, 
which allows the operator to get his/her fingers under the levers better 
and to obtain leverage prior to applying the ejection force. 
FIG. 5 shows a front view of front panel 114 which illustrates notches 111A 
and 111B that are in one side of front panel 114 and extend approximately 
4 mm toward the center of front panel 114. Slot 113A is laterally adjacent 
and vertically above notch 111A effectuated to receive eject finger 132A 
of lever 110A. Slot 113B is similarly placed laterally adjacent and 
vertically below notch 111B effectuated to receive eject finger 132B of 
lever 110B. Slots 113A and 113B are approximately 4.45 mm wide 
(represented by letter C in FIG. 5) by 15.07 mm in length (represented by 
the letter D in FIG. 5) and are approximately 4.24 mm from the top and 
bottom edges, (E in FIG. 5) respectively, of front panel 114, 
approximately 3.6 mm from the proximate side edge of front panel 114, (F 
in FIG. 5) and approximately 4.25 mm from the top and bottom edges of 
notches 111A and 111B, (G in FIG. 5) respectively. Accordingly, as 
inject/eject levers 110A and 110B are connected to module 112 on the back 
side of front panel 114, notches 111A and 111B and slots 113A and 113B 
permit levers 110A and 110B to pivot about the point of rotation 140. The 
position of notches 111 and slots 113 toward the farthest extreme corners 
of the front panel permit as much area as possible on the front panel to 
be used for electrical connections and graphical markings, which is 
becoming more and more important, especially as front terminal cards 
(shown in FIG. 6) are now capable of having more than 300 electrical 
connections, with the major present limitation being available space to 
accommodate the connections and wires. 
FIG. 6 illustrates a printed circuit module 190 that does not include front 
panel terminal card access and a printed circuit module 192 that includes 
front panel access 193 for electrical connection of a terminal card 194, 
which is more fully described and explained in related U.S. patent 
application Ser. No. 08/369,823, filed Jan. 6, 1995 to Robert Millard, 
entitled MASS TERMINATION OF SIGNALS FROM ELECTRICAL SYSTEMS TO DEVICES 
UNDER TEST, which is hereby incorporated for all that it teaches. 
FIGS. 3-6 illustrate an embodiment having two inject/eject levers 110A and 
110B at opposing ends of front panel 114. However, it will be readily 
appreciated that the present invention contemplates an embodiment 
comprising only one inject/eject lever, albeit an inferior embodiment in 
terms of mechanical advantage and stresses on module 112. It is to be 
further appreciated that the two inject/eject levers 110A and 110B are 
mirror images of each other in configuration and operation. Thus, a 
detailed description of inject/eject lever 110B will be sufficient to 
appreciate both inject/eject levers. 
The interrelationship between the components of the inject/eject system 
that are mounted on the plug-in module 112 is illustrated in FIG. 7. 
Specifically, a preassembled screw 150 with bearing and friction spring 
153 is inserted into the pivot aperture 140 of inject/eject lever 110B, 
inserted through module aperture 154 and is screwed into threaded aperture 
156 in support block 158. A screw 162 is inserted through aperture 164 in 
front panel 114 and screwed or otherwise secured in aperture 165 of 
support block 158. When inject/eject lever is secured to module 112 and 
front panel 114, lever arm 130 will extend through notch 111B and eject 
finger 132 will extend through slot 113B. The rest of the inject/eject 
lever 110B will be on the opposite side of front panel 114. This 
configuration will permit inject/eject lever 110B to pivot about the pivot 
aperture 140 whilst using the fewest number of components and taking up 
the least amount of useable area on the front panel and on the printed 
circuit module 112. 
Turning now to FIGS. 8-13, the inject/eject lever 110B will be explained in 
more detail. In particular, lever 110B comprises a lever arm 130 that has 
a width (H in FIG. 12) of approximately 3.2.+-.0.25 mm and a thickness of 
approximately 2.0.+-.0.25 mm at its tip. An upper side surface 183 of 
lever arm 130 remains relatively flat, while the lower side grasping 
surface 180 angles away from surface 183 (I in FIG. 10) at approximately 
14.degree..+-.0.5.degree. starting from a first end 202 and reaching a 
final thickness (J in FIG. 11) of approximately 4.77.+-.0.25 mm at a 
middle portion 204 before angling back down to approximately 3.2.+-.0.25 
mm at a second end 206 (K in FIG. 11), thus creating a grasping member of 
lever arm 130. At this point, the entire lever arm 130 begins to angle 
towards the pivotal aperture 140 at an angle of approximately 55.degree. 
(L in FIG. 11). In a preferred embodiment, a ledge 181 traverses the 
perimeter of the lever arm 130 on a first side of the end of said lever 
arm 130 (see FIGS. 9 and 11-13). The ledge 181 is approximately 
0.4.+-.0.25 mm in height (M in FIG. 13) and 1.0.+-.0.25 mm thick (N in 
FIG. 11). Due to manufacturing considerations, this ledge allows for 
radiused corners, as opposed to sharp corners, on the grasping portion of 
lever arm 130, as well as providing a grasping surface during operation, 
and may alternatively be on both sides of the lever arm i.e., ledge 181 
may also traverse a second side 184 of the lever arm 130. 
As the lever arm 130 reaches the pivotal axis portion of the lever 110B, it 
becomes a circular boss 141 having an outside diameter (O in FIG. 11) of 
approximately 10.32.+-.0.25 mm and being raised on the first side (Q in 
FIG. 12) by approximately 3.51.+-.0.25 mm. A first hole 143 is bored 
completely through the lever with the center of pivot aperture 140 having 
a diameter of approximately 5.3.+-.0.038 mm (R in FIG. 10). A second hole 
145 is bored from the second side of said lever to a depth of 
3.31.+-.0.076 mm with the same center as the first hole, having a diameter 
(S in FIG. 10) of approximately 6.85.+-.0.038 mm. This creates pivot 
aperture 140 that houses the bearing 150 and a bore area 145 that houses 
the screw head 153 and spring assembly when assembled (FIGS. 8 and 10). 
Two fingers (132 and 136) extend from the circular boss 141 on the second 
side of the lever 110B (FIGS. 9 and 11-13), creating a C-shaped bracket. 
Ejection finger 132 extends approximately 13.6.+-.0.25 mm from the center 
of pivot aperture 140 (T in FIG. 13) at approximately a 55.degree. angle 
(U in FIG. 11) from the lever arm 130 attached to the opposite side of the 
boss 141 (FIGS. 10 and 11). Injection finger 136 extends approximately 
10.5.+-.0.25 mm from the center of pivot aperture 140 (V in FIG. 12) at 
approximately a 164.degree. angle from the lever arm 130 attached to the 
opposite side of the boss 141 (FIGS. 10 and 11). Both the injection finger 
136 and the ejection finger 132 are hooked at their ends to form a 
C-shaped configuration in order to effectuate the engagement of injection 
bearing surface 126 and the ejection bearing surface 124 of mainframe 120, 
respectfully. Dimension X in FIG. 12 is the width of the lever arm 130 at 
the grasping end, which is 3.6.+-.0.25 mm. Dimension Y in FIG. 12 is the 
width of the lever across the boss 141 area, which is 6.97.+-.0.25 mm. 
Dimension Z is the length of the entire inject/eject lever, which is 
53.73.+-.0.25 mm. 
In a preferred embodiment, boss 141 will extend approximately an additional 
0.08 mm beyond the thickness of the two fingers 132 and 136 (see FIGS. 9 
and 13). This raised boss area 141 helps alleviate friction between the 
lever and the printed circuit module 112 when the operator applies a 
pivotal force to the lever during injection or ejection of the module 112 
(see FIG. 7). 
Lever 110 is preferably manufactured by a stainless steel 
metal-injection-molded process. As the VXIbus Consortium open standard 
calls for extruded aluminum injection/ejection bearing surfaces, the 
stainless steel will minimize galling of the injection and ejection 
bearing surfaces, both on the lever 110 and on the mainframe 120. However, 
any hard material could be used, including metals such as aluminum, and 
any known manufacturing process could be utilized such as machining or 
metal extrusion. It is preferable that the lever be made of a material 
different from that of the injection and ejection bearing surfaces of the 
mainframe, in order to minimize the possibility of galling on either 
surface. 
It is not intended to be exhaustive or to limit the invention to the 
precise form disclosed, and other modifications and variations may be 
possible in light of the above teachings. For example, the angles and 
dimensions of the preferred embodiment of the lever could be varied 
without departing from the overall concepts of the invention. The 
embodiment was chosen and described in order to best explain the 
principles of the invention and its practical application to thereby 
enable others skilled in the art to best utilize the invention in various 
embodiments and various modifications as are suited to the particular use 
contemplated. It is intended that the appended claims be construed to 
include other alternative embodiments of the invention except insofar as 
limited by the prior art.