BACKGROUND ART In general, the carbon dioxide content of air increases in a h ermetically sealed space with the passage of time because of breathing of living objects, and has detrimental effects on breathing. Accordingly, a ventilator is used to exchange contaminated indoor air for fresh outdoor air especially in a narrow space where a number of people stay such as an office or vehicle.

The ventilator includes an air blower for forcibly blowing indoor air and outdoor air, and repeats a process of externally discharging contaminated indoor air and internally sucking fresh outdoor air.

However, when cooling and ventilating operations are performed indoors at the same time, cooled indoor air is exhausted and hot outdoor air is sucked. Thus, a temperature of indoor air is higher than a cooling temperature, to reduce cooling efficiency. In the case that heating and ventilating operations are simultaneously performed indoors, heated indoor air is exhausted and cooled outdoor air is sucked.

As a result, the temperature of indoor air is lower than a heating temperature, to reduce heating efficiency.

Therefore, the ventilator further includes a heat exchanger for exchanging heat between indoor air and outdoor air.

In detail, according to Japanese Laid-Open Patent Application 11-287492 shown in F ig. 1, an outdoor air s uction hole 4 a for s ucking outdoor a ir and an

indoor air discharge hole 6b for discharging indoor air are formed on one surface of a rectangular casing 2, an outdoor air discharge hole 4b for discharging outdoor air and an indoor air suction hole 6a for sucking indoor air are formed on the other surface of the casing 2, a heat exchanger 8 for exchanging heat by forming passages for separately flowing indoor air and outdoor air is installed in the center of the casing 2 to cross the casing 2, and an air supply fan 10 and an air exhaust fan 20 are installed in both edges of the casing 2 to be positioned inside the outdoor air discharge hole 4b and the indoor air discharge hole 6b.

In addition, an air path for guiding outdoor air sucked from the outdoor air suction hole 4a to the heat exchanger 8 to be discharged to the outdoor air discharge hole 4b, and an air path for guiding indoor air sucked from the indoor air suction hole 6a to the heat exchanger 8 to be discharged to the indoor air discharge hole 6b are formed in the casing 2.

Here, the heat exchanger 8 is installed to be connected or disconnected through a checking hole 2a formed in the center of one surface of the casing 2.

Sirocco fans for sucking outdoor air or indoor air in the axial direction and discharging sucked air in the radius direction are used as the air supply fan 20 and the air exhaust fan 20. The air supply fan 10 and the air exhaust fan 20 are installed to be positioned inside fan housings 12 and 22, respectively. Motors 14 and 2 4 f or d riving the a ir supply f an 10 a nd the a ir exhaust f an 2 0 are f ixedly installed in the fan housings 12 and 22, respectively.

The motor 14 for driving the air supply fan 10 is installed toward the indoor air suction hole 6a, and the motor 24 for driving the air exhaust fan 20 is installed toward t he o utdoor a ir suction h ole 4a. Accordingly, the m otors 14 a nd 2 4 a re installed in the facing direction.

However, in the conventional ventilator, the motors 14 and 24 for driving the

air supply fan 10 and the air exhaust fan 20 are installed in both edges of the casing 2 in the checking hole2a installation direction and the facing direction to the checking hole2a installation direction, respectively, so that an operator can disconnect merely the fans and motors installed in the checking hole2a installation direction through the checking hole 2a. It is thus difficult to examine and repair the air supply fan 10, the air exhaust fan 20 and the motors 14 and 24.

On the other hand, as disclosed in Japanese Laid-Open Patent Application 09-137984 shown in Figs. 2 and 3, an outdoor air suction hole 34a for sucking outdoor air and an i ndoor air discharge hole 3 6b for discharging i ndoor air are formed on one surface of a rectangular casing 32, an outdoor air discharge hole 34b for discharging outdoor air and an indoor air suction hole 36a for sucking indoor air are formed on the other surface of the casing 32, a heat exchanger 38 for forming passages for separately flowing outdoor air and indoor air is installed in the center of the casing 32 to cross the casing 32, and an air supply fan 40 for sucking outdoor air and an air exhaust fan 50 for discharging indoor air are installed in the center of one surface of the casing 32 and the center of the other surface of the casing 32, respectively.

In addition, partitioning units 37a and 37b for guiding outdoor air sucked from the outdoor air suction hole 34a to the heat exchanger 38, or guiding indoor air sucked from the indoor air suction hole 36a to the heat exchanger 38 are installed in the casing 32, and ducts 39a and 39b for guiding outdoor air passing through the heat exchanger 38 to be discharged to the outdoor air discharge hole 34b, or guiding indoor air passing through the heat exchanger 38 to be discharged to the indoor air discharge hole 36b are installed in the casing 32, to form air paths for separately flowing outdoor air and indoor air.

The heat exchanger 38 is installed in the casing 32 to be connected or

disconnected through a checking hole 32a formed in the center of one surface of the casing 32. The edges of the heat exchanger 38 are slidably fixed into rails 35 formed in both ends of the partitioning units 37a and 37b and the top and bottom inside surfaces of the casing 32.

Sirocco fans for sucking outdoor air or indoor air in the axial direction and discharging sucked air in the radius direction are used as the air supply fan 40 and the air exhaust fan 50. The air supply fan 40 and the air exhaust fan 50 are installed inside fan housings 42 and 52 connected to the ducts 39a and 39b, respectively. Motors 44 and 54 for driving the air supply fan 40 and the air exhaust fan 50 are fixedly installed in the fan housings 42 and 52, respectively.

Here, the motor 44 for driving the air supply fan 40 and the motor 54 for driving the air exhaust fan 50 are installed toward both side centers of the heat exchanger 38.

In the conventional ventilator, the motors 44 and 54 for driving the air supply fan 40 and the air exhaust fan 50 are positioned to face the heat exchanger 38 in both side centers of the casing 30. Accordingly, when an operator disconnects the motors 44 and 54 for respectively driving the air supply fan 40 and the air exhaust fan 50 through the checking hole 32a, the motors 44 and 54 are bumped into the rails 35 for connecting or disconnecting the heat exchanger 38, and thus not completely disconnected from the casing 32. It is thus difficult to examine and repair the air supply fan 40, the air exhaust fan 50 and the motors 44 and 54.

According to Japanese Laid-Open Patent Application 07-332727 shown in Fig. 4, an outdoor air suction hole 64a and an indoor air discharge hole 66b are formed on one surface of a casing 62, and an outdoor air discharge hole 64b and an indoor air suction hole 66a are formed on the facing surface of the casing 62.

The outdoor air suction hole 64a and the indoor air suction hole 66b are formed to

face each other, and the outdoor air discharge hole 64b and the indoor air discharge hole 66b are formed to face each other. A heat exchanger 68 for exchanging heat between outdoor air and indoor air is installed in the casing 62 to cross the casing 62.

Here, air paths for flowing outdoor air sucked from the outdoor air suction hole 64b to one side of the heat exchanger 68 and indoor air discharged from one side o f t he h eat e xchanger 6 8 t o t he indoor a ir d ischarge h ole 66b in d ifferent spaces, and flowing indoor air sucked from the indoor air suction hole 66a to the other side of the heat exchanger 68 and outdoor air discharged from the other side of the heat exchanger 68 to the outdoor air discharge hole 64b in different spaces are f ormed in the casing 6 2. A n a ir supply f an 7 2 and a m otor 7 4 f or b lowing outdoor air are installed inside the outdoor air discharge hole 64b, and an air exhaust fan 82 and a motor 84 for blowing indoor air are installed inside the indoor air discharge hole 66b.

Especially, a checking hole 62a is formed on one side surface of the casing 62 to check inside components, the heat exchanger 68 is installed to be slidably connected or disconnected through the checking hole 62a, and a pair of guide rails 78 and 88 for moving the motors 74 and 84 to the checking hole 62a to disconnect the motors 74 and 84 through the checking hole 62a for checking are installed in both sides of the heat exchanger 68.

Here, the air supply fan 72 is installed in a fan housing 71 formed inside the outdoor air discharge hole 64b for guiding air flow, the top and bottom edges of the fan housing 71 are installed to move to the checking hole 62a along the guide rail 78 of the outdoor air discharge hole64b side, and the motor 74 for driving the air supply fan 72 is fixed to the fan housing 71 by a motor supporting member 76.

Identically to the air supply fan 72, the air exhaust fan 82 is installed in a fan

housing 81, the fan housing 81 is installed to move to the checking hole 62a along the guide rail 88 of the indoor air discharge hole66b side, and the motor 84 for driving the air exhaust fan 82 is fixed to the fan housing 81 by a motor supporting member 86.

The guide rails 78 and 88 are formed to guide the top and bottom ends of the fan housings 71 and 81, vertically to the length direction of the heat exchanger 68.

On the other hand, the motors 74 and 84 are installed adjacent to one surface of the casing 62 where the checking hole 62a has been formed, to remove an unnecessary space of the casing 62 and reduce the whole size of the product.

In this ventilator, the guide rails 78 and 88 are installed in both sides of the heat exchanger 68 vertically to the heat exchanger 68, the fan housings 71 and 81 are installed to move along the guide rails 78 and 88, and the motors 74 and 84 fixed to the fan housings 71 and 81 are transferred to the checking hole 62a and disconnected. Accordingly, the operator can easily maintain and repair the motors 74 and 84. However, it is difficult to embody such a ventilator. Furthermore, the production cost is raised due to increase of the constitutional components. Even if the fan housings 71 and 81 are installed closely to the discharge holes 64b and 66b, air leakage increases without a special sealing process, to reduce air flow efficiency. As a whole, efficiency of the system decreases.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a ventilator which allows an operator to easily disconnect an air supply fan, an air exhaust fan and motors through a checking hole formed on one side surface of a casing and easily maintain and repair the fans and motors, by changing installation directions of the

fans and motors without using additional components.

In order to achieve the above-described object of the invention, there is provided a ventilator including: a casing having an outdoor air suction hole for sucking outdoor air and an indoor air discharge hole for discharging indoor air on its one surface, an outdoor air discharge hole for discharging outdoor air and an indoor air suction hole for sucking indoor air on its facing surface, and a checking hole for checking inside components on its side surface; a heat exchanger installed in the center of the casing, for forming first and second passages for separately flowing outdoor air and indoor air, and exchanging heat; an air supply fan installed on the passages for flowing outdoor air, for internally sucking outdoor air; an air exhaust fan installed on the passages for flowing indoor air, for extemally discharging indoor air; and motors installed toward the surface of the casing where the checking hole has been formed with a connection or disconnection space in the length direction of the heat exchanger, for driving the air supply fan and the air exhaust fan, respectively.

According to one aspect of the invention, the ventilator further includes fan housings having the air supply fan and the air exhaust fan inside to blow outdoor air or indoor air, wherein first orifice units are incorporated on the front surfaces of the fan housings, second orifice units are installed on the rear surfaces of the fan <BR> <BR> housings to b e connected o r d isconnected, a nd m otor s upporting m embers for supporting the motors are fixedly installed in the second orifice units. The circumferences of the second orifice units are fixed to the rear opened surfaces of the fan housings by screws.

According to another aspect of the invention, the outdoor air discharge hole is formed in the center of one surface of the casing, the indoor air discharge hole is formed in the center of the facing surface of the casing, the indoor air suction hole

is formed in one side of one surface of the casing, and the outdoor air suction hole is formed in the other side of the facing surface of the casing.

According to yet another aspect of the invention, the checking hole is formed in the center of one side surface of the casing adjacent to the outdoor air suction hole and the indoor air discharge hole, the air supply fan is installed inside the outdoor air discharge hole, and the air exhaust fan is installed inside the indoor air discharge hole.

According to yet another aspect of the invention, the heat exchanger is installed in the casing to be slidably connected or disconnected through the checking hole in the length direction, and the motors are installed to have their rotation axes parallel to the length direction of the heat exchanger.

According to yet another aspect of the invention, an outdoor air passage guide for guiding outdoor air sucked from the outdoor air suction hole to the first passages of the heat exchanger, and guiding indoor air discharged from the second passages of the heat exchanger to the indoor air discharge hole is formed in the casing. The outdoor air passage guide includes a convex unit, a part of which connected to the outdoor air suction hole being protruded, and a concave unit, a part of which connected to the indoor air discharge hole being caved. The air exhaust fan and the motor for driving the air exhaust fan are installed in the concave unit, and the motor for driving the air exhaust fan maintains a predetermined interval from the convex unit of the outdoor air passage guide for connection or disconnection.

According t o yet a nother a spect of t he invention, a n i ndoor a ir p assage guide for guiding indoor air sucked from the indoor air suction hole to the second passages of the heat exchanger is formed in the casing. The indoor air passage guide includes a convex unit, a part of which connected to the indoor air suction

hole being protruded, and a concave unit, a part of which connected to the outdoor air discharge hole being caved. The air supply fan and the motor for driving the air supply fan are installed in the concave unit, and the motor for driving the air supply fan maintains a predetermined interval from adjacent one side surface of the casing for connection or disconnection.

Here, the motor supporting members and the second orifice units are installed in parallel to the length direction of the heat exchanger, so that the heat exchanger can be connected or disconnected in the sliding connection or disconnection direction.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become better understood with reference to the accompanying drawings which are given only by way of illustration and thus are not limitative of the present invention, wherein: Fig. 1 is a perspective view illustrating one example of a conventional ventilator ; Fig. 2 is a perspective view illustrating another example of the conventional ventilator ; Fig. 3 is a cross-sectional view illustrating another example of the conventional ventilator; Fig. 4 is a plan view illustrating yet another example of the conventional ventilator ; Fig. 5 is a perspective view illustrating a ventilator in accordance with the present invention; Fig. 6 is a plan view illustrating the ventilator in accordance with the present invention;

Fig. 7 is a cross-sectional view taken along line A-A of Fig. 6; Fig. 8 is a cross-sectional view taken along line B-B of Fig. 6; and Figs. 9 and 10 are perspective views illustrating disassembly of an air blowing apparatus of the ventilator in accordance with the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

Figs. 5 and 6 are a perspective view and a plan view illustrating a ventilator in accordance with the present invention, Figs. 7 and 8 are cross-sectional views taken along lines A-A and B-B of Fig. 6, and Figs. 9 and 10 are perspective views illustrating disassembly of an air blowing apparatus of the ventilator in accordance with the present invention.

Referring to Figs. 5 and 6, the ventilator includes a rectangular casing 162 having a predetermined height, an outdoor air suction hole 164a for sucking outdoor air and an indoor air discharge hole 166b for discharging indoor air which are formed on one surface of the casing 162, an outdoor air discharge hole 164b for discharging outdoor air and an indoor air suction hole 166a for sucking indoor air which are formed on the facing surface to one surface of the casing 162 where the outdoor air suction hole 164a and the indoor air discharge hole 166b have been formed, a checking hole 162a formed on one side surface of the casing 162, for checking inside constitutional elements, an air supply fan 170 installed on passages for flowing outdoor air, for internally sucking outdoor air, an air exhaust fan 180 installed on passages for flowing indoor air, for externally discharging indoor air, and motors 174 and 184 installed toward one side surface of the casing 162 where the checking hole 162a has been formed with a predetermined

connection or disconnection space for easy disconnection, for driving the air supply fan 170 and the air exhaust fan 180.

The ventilator further includes a heat exchanger 168 installed in the casing 162 to be slidably connected or disconnected through the checking hole 162a of the casing 162, for forming first and second passages for separately flowing outdoor air and indoor air, and exchanging heat between outdoor air and indoor air.

Here, the heat exchanger 168 is manufactured by stacking heat exchange units 1 68A a nd 1 68B including a p lurality o f g uide ribs 1 68b on rectangular o r hexagonal heat exchange films 168a. The heat exchange units 168A and 168B are divided into a first heat exchange unit 168A for flowing outdoor air and a second heat exchange unit 168B for flowing indoor air according to the installation directions of the guide ribs 168b on the heat exchange films 168a. The first and second heat exchange units 168A and 168B are alternately stacked.

Accordingly, the first passages for guiding air to be sucked from the bottom of one side surface and discharged to the top of the other side surface, and the second passages for guiding air to be sucked from the bottom of the other side surface and discharged to the top of one side surface are formed in the heat exchanger 168.

In the casing 162, an outdoor air passage guide 192 for guiding outdoor air sucked from the outdoor air suction hole 164a to the first passages of the heat exchanger 168 is installed in one side of the heat exchanger 168, and an indoor air passage guide 194 for guiding indoor air sucked from the indoor air suction hole 166a to the second passages of the heat exchanger 168 is installed in the other side of the heat exchanger 168.

In the outdoor air passage guide 192, a convex unit for guiding outdoor air from the outdoor air suction hole 164a to be sucked to the first passages of the

heat exchanger 168 is upwardly protruded, and a concave unit for guiding indoor air from the second passages of the heat exchanger 168 to be discharged to the indoor air discharge hole 166b is downwardly caved. The convex unit is connected to the outdoor air suction hole 164a and the concave unit is connected to the indoor air discharge hole 166b.

In addition, in the indoor air passage guide 194, a convex unit for guiding indoor air from the indoor air suction hole 166a to be sucked to the second passages of the heat exchanger 168 is upwardly protruded, and a concave unit for guiding outdoor air from the first passages of the heat exchanger 168 to be discharged to the outdoor air discharge hole 164b is downwardly caved. The convex unit is connected to the indoor air suction hole 166a and the concave unit is connected to the outdoor air discharge hole 164b.

The checking hole 162a is formed in the center of one side surface of the casing 162 adjacent to the outdoor air suction hole 164a and the outdoor air discharge hole 164b, and the heat exchanger 168 is installed in the casing 162 to be connected or disconnected through the checking hole 162a. Here, guide protrusions 169a and 169b protruded long in the length direction in both sides of the heat exchanger 168 are guided to guide grooves 196 and 198 formed long in the length direction in the end of the outdoor air passage guide 192 and the end of the indoor air passage guide 194, so that the heat exchanger 168 can be slidably connected or disconnected. In addition, the top and bottom ends of the heat exchanger 168 are positioned in guide grooves 165 formed long in the length direction on the top and bottom inside surfaces of the casing 162, so that the heat exchanger 168 can be slidably connected or disconnected.

The guide protrusions 169a and 169b of the heat exchanger 168 are inserted into the guide grooves 196 and 198, and thus air leakage is prevented

between the heat exchanger 168 and the outdoor air passage guide 192 and the indoor air passage guide 194. The top and bottom ends of the heat exchanger 168 are inserted into the guide grooves 165, and thus air leakage is prevented between the top and bottom ends of the heat exchanger 168 and the casing 162.

On the other hand, in order to evenly flow outdoor air or indoor air on the whole surface of the heat exchanger 168, the outdoor air discharge hole 164b is formed in the center of one surface of the casing 162, and the indoor air discharge hole 166b is formed in the center of the facing surface (the other surface) to the surface of the casing 162 where the outdoor air discharge hole 164b has been formed. The air supply fan 180 is installed in the concave unit of the indoor air passage guide 194 inside the outdoor air discharge hole 164b, and the air exhaust fan 190 is installed in the concave unit of the outdoor air passage guide 192 inside the indoor air discharge hole 166b.

Here, the indoor air suction hole 166a is close to one side of one surface of the casing 162, and the outdoor air suction hole 164a is close to the other side of the facing surface (the other surface) to the surface of the casing 162 where the indoor air suction hole 166a has been formed. Therefore, indoor air and outdoor air are sucked from the facing surfaces in the diagonal directions, and discharged to the centers, to lengthen the passages.

Accordingly, when the air supply fan 170 and the air exhaust fan 180 are operated, as shown in Fig. 7, outdoor air is internally sucked through the outdoor air suction hole 1 64a, t he h eat exchanger 168, the a ir s upply f an 170 a nd the outdoor air discharge hole 164b, and as shown in Fig. 8, indoor air is extemally discharged through the indoor air suction hole 166a, the heat exchanger 168, the air exhaust fan 180 and the indoor air discharge hole 166b. Indoor air and outdoor air flow in the heat exchanger 168 in the facing directions, to exchange heat.

Especially, sirocco fans for obtaining high air flow in a relatively small suction area are used as the air supply fan 170 and the air exhaust fan 180. The sirocco fans are installed in fan housings 172 and 182 to discharge air sucked in the axial direction to the radius direction.

In detail, the fan housings 172 and 182 including the air supply fan 170 and the air exhaust fan 180 inside will now be explained with reference to Figs. 9 and 10. The fan housings 172 and 182 include first orifice units 172a and 182a having inlet holes 172h and 182h in their centers to guide air flow on the front surfaces, fan housing main bodies 172A and 182A having their rear surfaces opened, and second orifice units 172B and 182B being installed on the rear surfaces of the fan housing main bodies 172A and 182A to be connected or disconnected, and having inlet holes 172h and 182h in their centers to suck air.

Here, the fan housing main bodies 172A and 182A include o utlet h oles 172H and 182H linked to the outdoor air discharge hole 164b or the indoor air discharge hole 166b, so that outdoor or indoor air can be sucked in the axial direction through the inlet holes 172h and 182h of the first and second orifice units 172a and 182a and discharged in the radius direction to the outlet holes 172H and 182H.

Motor fixing members 176 and 186 having fixing holes 176h and 186h in their centers to fix motor fixing units 174a and 184a formed in the circumferences of the motors 174 and 184 are fixedly installed in the second orifice units 172B and 182B.

In the fan housing main bodies 172A and 182A, the circumferences of the outlet holes 172H and 182H are fixed to the outdoor air discharge hole 164b or the indoor air discharge hole 166b by screws, the circumferences of the second orifice units 172B and 182B are fixed to the rear surfaces of the fan housing main bodies

172A and 182A by screws, the top and bottom ends of the motor supporting members 176 and 186 are fixed to the second orifice units 172B and 182B by screws, and the motor fixing units 174a and 184a of the motors 174 and 184 are fixed to the motor supporting members 176 and 186 by screws.

The motors 174 and 184 are installed to have their rotation axes parallel to the length direction of the heat exchanger 168 with a predetermined connection or disconnection space in the length direction, so that the motors 174 and 184 can be easily connected or disconnected through the checking hole 162a in the length direction of the heat exchanger 168. That is, the motors 174 and 184 are installed to have a predetermined interval from the other adjacent component (for example, convex unit of the outdoor air passage guide 192, convex unit of the indoor air passage guide 194, or one side surface of the casing 162 where the checking hole 162a has been formed).

The assembly process of the air supply fan 170, the air exhaust fan 180, the fan housings 172 and 182 and the motors 174 and 184 will now be explained. The fan housing main bodies 172A and 182A are installed vertically to one surface of the casing 162 where the outdoor air discharge hole 164b has been formed, and the other surface of the casing 162 where the indoor air discharge hole 166b has been formed. Here, the rear surfaces of the fan housing main bodies 172A and 182A are installed toward one side surface of the casing 162 where the checking hole 162a has been formed.

Thereafter, the motors 174 and 184 are coupled to the motor supporting members 176 and 186 by screws, the second orifice units 172B and 182B are inserted into the rotation axes of the motors 174 and 184, the air supply fan 170 and the air exhaust fan 180 are connected to the ends of the rotation axes of the motors 174 and 184, and the motor supporting members 176 and 186 are fixed to

the second orifice units 172B and 182B by screws, to compose fan assemblies.

The fan assemblies are assembled on the rear surfaces of the fan housing main bodies 172A and 182A to be connected or disconnected in the sliding connection or disconnection direction of the heat exchanger 168. The second orifice units 172B and 182B are fixed to the circumferences of the fan housing main bodies 172A and 182A by screws.

In the case that the fan assemblies are connected or disconnected to/from the fan housing main bodies 172A and 182A, the fan assemblies are not bumped into any one of the outdoor air passage guide 192, the indoor air passage guide 194 or one side surface of the casing 162 where the checking hole 162a has been formed because of the connection or disconnection space. The space can be obtained by changing the shape of the outdoor air passage guide 192 or the indoor air passage guide 194, or maintaining a predetermined interval between one side surface of the casing 162 where the checking hole 162a has been formed, the outdoor air suction hole 164a and the outdoor air discharge hole 164b.

As a result, when the operator examines or repairs the air supply fan 170, the air exhaust fan 180 and the motors 174 and 184, he/she disconnects the heat exchanger 168 through the checking hole 162a, separates the second orifice units 172B and 182B from the fan housing main bodies 172A and 182A, disconnects the fan assembly including the air supply fan 170 and motor 174 or the-air exhaust fan 180 and motor 184 from the fan housing main bodies 172A and 182A, and takes the fan assembly from the casing 162 through the checking hole 162a at a time, thereby easily examining and repairing the components.

The ventilator was explained in detail on the basis of the embodiments and accompanying drawings of the present invention. However, it is understood that the present invention should not be limited to these preferred embodiments but various changes and modifications can be made by one skilled in the art within the spirit and scope of the present invention as hereinafter claimed.