Apparatus for performing multiple functions in a data storage device using a single electro-mechanical device

Description of equivalent WO 9612279 A1

APPARATUS FOR PERFORMING MULTIPLE FUNCTIONS IN A DATA STORAGE DEVICE USING A SINGLE ELECTRO-MECHANICAL DEVICE

BACKGROUND

Field of the Invention The present invention relates to a data storage device of the type that accepts a removable disk cartridge, and more particularly, to a low cost mechanism for performing multiple functions in a data storage device.

Description of the Prior Art Removable disk cartridges for storing digital electronic information typically comprise an outer casing or shell that houses a rotatable recording medium, or disk, upon which electronic information can be stored. The cartridge shell often comprises upper and lower halves that are joined together to house the disk. The disk is mounted on a hub that rotates freely within the cartridge. When the cartridge is inserted into a data storage device, e.g., disk drive, a spindle motor in the drive engages with the disk hub in order to rotate the disk within the cartridge. The outer shell of the cartridge typically has some form of opening near its forward edge to provide the recording heads of the drive with access to the recording surfaces of the disk. A shutter or door mechanism is often provided to cover the opening when the cartridge is not in use to prevent dust or other contaminants from entering the cartridge and settling on the recording surface of the disk.

Data storage devices, e.g. disk drives, for receiving removable disk cartridges perform a number of functions incident to the recording and/or retrieval of information from a disk cartridge. For example, two very critical functions are: (i) to latch or hold the cartridge in place during operation, releasing and ejecting the cartridge only at an appropriate time and only under certain conditions, and (ii) locking the read/write heads of the disk drive in place to prevent movement of the heads under inappropriate circumstances. Prior art disk drives typically treat these and other functions separately, often including multiple electro-mechanical devices to perform each function. Use of multiple electro-mechanical devices increases the cost and complexity of these prior art disk drives. Cost concerns sometimes force the data storage device designer to include manually operated mechanisms that may make the data storage device less user-friendly. Consequently, there is a need for a data storage device, or disk drive, having apparatus for performing multiple functions in a simpler, more cost effective manner. The present invention satisfies this need.

SUMMARY OF THE INVENTION

The present invention is directed to a data storage device, or disk drive, for receiving a removable disk cartridge. According to the present invention, the data storage device of the present invention comprises first and second members movably mounted in the data storage device. Each movable member is adapted to perform a respective function within the disk drive. A first spring is coupled to the first movable member for biasing the first movable member in a first direction, and a second spring is coupled to the second movable member for biasing the second movable member in the same direction. The first spring has a stronger biasing force than the second spring. A single electro¬ mechanical device having a drive shaft adapted to move from an extended position to a retracted position in response to an electrical current is mounted in the data storage device. The drive shaft has an operating end adapted to engage the first and second movable members and to move the members against their respective biasing forces as the drive shaft moves along a path of travel from its extended position to its retracted position. The operating end of the drive shaft is adapted to engage the second member and to move the second member a predetermined distance to an intermediate position of the drive shaft before engaging the first member. The electro-mechanical device is responsive to a first current sufficient to move the drive shaft against the biasing force of the second spring but insufficient to move the drive shaft against the biasing force of the first spring. The electro¬ mechanical device is responsive to a second current, greater than the first current, that is sufficient to move the drive shaft against the combined biasing forces of both springs. When an electrical signal having the first current is applied to the electro-mechanical device, the drive shaft of the device will begin to move from its extended position toward its retracted position. Because the first current is sufficient to overcome the biasing force of the second spring, the operating end of the drive shaft will engage the second movable member and begin to move the second member against its biasing force. However, when the drive shaft reaches an intermediate position in which the operating end of the drive shaft begins to engage the first movable member, the drive shaft will stop since the first current is insufficient to overcome the biasing force of the first spring. In this manner, the first current can be applied to move the second member independently of the first member. When it is desired to move the first member, the second current can be applied to the electro-mechanical device. Because the second current is sufficient to overcome the combined biasing forces of the first and second springs, the operating end of the drive shaft will move past the intermediate position to its fully retracted position, thereby moving the first movable member against the biasing force of the first spring.

Preferably, the single electro-mechanical device comprises a single solenoid having a single drive shaft with an operating end. Additionally, in a preferred embodiment of the present invention, the first movable member and the second movable member each have a respective projection formed thereon. The respective projections are disposed relative to the operating end of the drive shaft such that, during movement of the drive shaft from its extended position to its retracted position, the drive shaft engages the projection on the second movable member and moves the second movable member a predetermined distance to the intermediate position of the drive shaft prior to engaging the projection on the first movable member. Preferably, a portion of the drive shaft of the electro-mechanical device is cut-away to form a channel in which the projections on the first and second movable members can move. This allows the first and second movable members to be operated independently of the operating end of the drive shaft.

In one implementation of the present invention, the data storage device includes an eject member that engages with the disk cartridge and moves from a forward position to a rearward position upon insertion of the disk cartridge into the device, and an actuator movably mounted within the data storage device for moving a read/write head of the data storage device over a recording medium in the disk cartridge. In this implementation, the first movable member comprises an eject latch lever adapted to releasably latch the eject member in the rearward position to maintain the disk cartridge in the data storage device. The second movable member comprises a head locking lever operative to releasably engage the actuator to lock the actuator in place and prevent movement thereof.

The foregoing and other objects, features and advantages of the invention will become evident hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS The foregoing summary, as well as the following detailed description of the preferred embodiment, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings an embodiment that is presently preferred, it being understood, however, that the invention is not limited to the specific methods and instrumentalities disclosed. In the drawings: Figure 1 is a perspective view of a data storage device, or disk drive, in which the present invention is embodied;

Figure 2 is a perspective view of a disk cartridge for use with the disk drive of the Figure 1; Figure 3 is a bottom view of the disk cartridge of

Figure 2;

Figure 4 is a top view of the data storage device of Figure 3 with a top cover of the device housing removed; Figures 5-7 are top views of the data storage device of Figure 4 illustrating the insertion of a disk cartridge into the device;

Figure 8 illustrates further details of a portion of the data storage device of Figure 3;

Figures 9-12 illustrate further details of the operation of a first movable member and a second movable member in accordance with the present invention; and

Figure 13 is a circuit for applying two different currents to a solenoid.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings wherein like numerals indicate like elements throughout, there is shown in Figure 1 a data storage device, or disk drive 40, in which the present invention is embodied. As shown, the disk drive 40 comprises an outer housing 42 having top and bottom covers 44, 46 and a front panel 48. A disk cartridge can be inserted into the disk drive 40 through a horizontal opening 51 in the front panel 48 of the disk drive 40. An eject button is also provided on the front panel for automatically ejecting a disk cartridge from the disk drive 40. The disk drive 40 can be employed as a stand-alone unit, or alternatively, can be employed as an internal disk drive of a computer (not shown) . Figures 2 and 3 show an exemplary disk cartridge 10 adapted for use in the disk drive 40 of Figure 1. As shown, the disk cartridge 10 comprises an outer casing 12 having upper and lower shells 22, 24 that mate to form the casing. A disk-shaped recording medium 14 is affixed to a hub 16 that is rotatably mounted in the casing 12. An opening 21 on the bottom shell 24 of the casing 12 provides access to the disk hub 16. A head access opening 30 in the front peripheral edge 20 of the disk cartridge 10 provides access to the recording surfaces of the disk 14 by the recording heads of the disk drive. A shutter 18 (not shown in Fig. 2) is provided on the front peripheral edge 20 of the disk cartridge 10 to cover the head access opening 30 when the cartridge is not in use. When the cartridge is inserted into the disk drive, the shutter 18 moves to the side exposing the head access opening 30 and thereby providing the heads of the drive with access to the recording surface of the disk 14. In the present embodiment, the casing houses a flexible or floppy magnetic disk, however, in other embodiments, the disk may comprise a rigid magnetic disk, a magneto-optical disk or an optical storage medium.

The opposite front corners of the disk cartridge 10 have a non-square shape defined by angled surfaces 20c, 20d that angle away from the front peripheral edge 20 of the cartridge at a predetermined angle. Additionally, a pair of projections 20a, 20b are formed on the front peripheral edge 20 of the cartridge. Each projection 20a, 20b is formed adjacent a respective one of the angled surfaces 20c, 20d at the point where the respective surface 20c, 20d begins to angle away from the plane of the front peripheral edge 20 of the cartridge 10. Figure 4 is a top view of the disk drive 40 of Figure 1 with the top cover 44 removed. The disk drive 40 comprises an internal platform 50 that slides along opposing side rails 52, 54 between a forward position (Fig. 4) and a rearward position (Fig. 7) . A pair of springs 56, 58 bias the platform 50 toward its forward position.

An actuator 60, which in the preferred embodiment comprises a linear actuator, is mounted to the rear of the platform 50. The linear actuator 60 comprises a carriage assembly 62 having two lightweight flexible arms 64, 66. The recording heads 18, 19 of the disk drive are mounted at the ends of the respective arms 64, 66. A coil 68, which is part of a voice coil motor, is mounted at the opposite end of the carriage 62. The coil 68 interacts with magnets (not shown) to move the carriage linearly so that the heads 18 and 19 can move radially over respective recording surfaces of a disk cartridge inserted into the disk drive. Additional details of the linear actuator 60 are provided in co-pending application Serial No. 08/324,599, filed concurrently herewith, entitled "Actuator for Data Storage Device"

(Attorney Docket IOM-8908) , which is incorporated herein by reference.

A raised wall 53 is formed on the platform. The raised wall 53 extends across the width of the platform 50, perpendicularly to the direction of motion of the carriage 62. The raised wall 53 defines an eject member that engages the front peripheral edge 20 of the disk cartridge 10 upon insertion of the disk cartridge into the disk drive. The opposite side edges 55a, 55b of the eject member 53 are angled in the same manner as the opposite front corners 20c, 20d of the disk cartridge 10. Thus, the shape of the eject member 53 mirrors the contour of the forward end face of the cartridge. As further shown, the front surface of the eject member 53 has a pair of projections 53a, 53b positioned near the angled surfaces 55a, 55b.

The disk drive 40 further comprises a spindle motor 82 capable of rotating the recording medium of a disk cartridge at a predetermined operating speed. In the present embodiment, the spindle motor 82 is coupled to the platform 50. As described hereinafter, when a disk cartridge is inserted into the disk drive, the hub 16 of the disk cartridge engages the spindle motor 82 of the disk drive 40 when the platform reaches its rearward position.

According to the present invention, as embodied in the disk drive 40 illustrated herein, the disk drive 40 comprises a first movable member movably mounted in the disk drive for performing a respective function. In the embodiment described herein, the first movable member comprises an eject latch lever 70 movably mounted within the disk drive 40. As described hereinafter, the eject latch lever 70 functions to releasably latch the platform 50 in its rearward position. In the present embodiment, the eject latch lever 70 is pivotally mounted on the platform 50 about a rotation shaft 70b. A first spring 90 (Figs. 8-10) is coupled to the eject latch lever 70 (i.e., first movable member) at the rotation shaft 70b in order to bias the lever 70 in a first direction (e.g., the X* direction). The eject latch lever 70 has a cutout 70a adapted to releasably engage a latch projection 78 as the platform 50 (see Fig. 6) moves backward into its rearward position. The biasing force of the first spring 90 urges the eject latch lever 70 into this latched position. In the preferred embodiment, the latch projection 78 is formed as part of the top cover 44 (not shown) of the disk drive 40.

Further in accordance with the present invention, the disk drive 40 comprises a second movable member movably mounted within the disk drive 40. In the embodiment described herein, the second movable member comprises a head locking lever 72 that is pivotally mounted on the platform 50 about a rotation shaft 72b. As described hereinafter, the head locking lever 72 functions to lock and unlock the carriage 62 of the linear actuator 60. A second spring 92 (Figs. 8-10) is coupled to the head locking lever 72 (i.e., second movable member) at its rotation shaft 72b to bias the head locking lever 72 in the same direction as the eject latch lever 70 (i.e., the X⁺ direction) . An end 72a of the head locking lever, which extends at a right angle to the main shaft of the lever 72, is adapted to releasably engage an end 62a of the actuator carriage 62 when the carriage 62 is in a fully retracted position, thereby locking the carriage in place and preventing inadvertent movement of the recording heads 18, 19.

A single electro-mechanical device, which in the preferred embodiment comprises a solenoid 74, is mounted on the platform 50 and has a drive shaft 76. When the solenoid 74 is energized by an electrical current, the drive shaft 76 moves in the X" direction from a normally extended position toward a retracted position. As the drive shaft 76 of the solenoid 74 moves toward its retracted position, an enlarged operating end 76a of the drive shaft 76 engages the first and second movable members (e.g., eject latch and head locking levers 70, 72) in order to pull the members in the X^" direction against the respective biasing forces of the first and second springs 90, 92. Additional details of the structure and operation of the solenoid 74 and the movable members in accordance with the present invention are provided hereinafter with reference to Figures 9-12.

Figures 5-7 illustrate the insertion of a disk cartridge 10 into the disk drive 40. For purposes of illustration only, some components of the disk drive 40 are not shown. Referring to Figure 5, a disk cartridge 10 is inserted into the disk drive 40 through the opening 51 in the front panel 48 of the disk drive 40. Initially, the platform 50 is in its forward position, as shown. As the disk cartridge 10 is pushed farther into the disk drive 40, the pair of projections 20a, 20b on the forward end 20 of the cartridge 10 engage the corresponding pair of projections 53a, 53b on the front surface of the eject member 53 of the platform 50. Thereafter, the disk cartridge 10 and platform 50, including the eject member 53, move together rearwardly against the biasing force of the springs 56, 58 (Fig. 4) . The platform 50 rides in slots (not shown) along the opposing side rails 52, 54. The slots (not shown) in the opposing side rails 52, 54 are contoured such that, as the platform 50 and disk cartridge 10 move rearwardly, the elevation of the platform 50 changes. Specifically, the platform 50 rises in order to bring the spindle motor 82 of the disk drive 40 into engagement with the hub 16 of the disk cartridge 10. Engagement of the hub 16 and spindle motor 82 is completed when the platform 50 reaches its final rearward position (Fig. 7) .

Referring to Figure 6, as the platform 50 approaches its rearward position, the portion of the eject latch lever 70 just rearward of the cutout 70a contacts an angled surface 78a of the latch projection 78. As the disk cartridge 10 pushes the platform 50 farther to the rear of the disk drive, the eject latch lever 70 rides along the angled surface 78a pushing the eject latch lever 70 to the side (i.e., X^" direction) against its normal spring bias. As shown in Figure 7, when the platform reaches its full rearward position, the eject latch lever 70 springs back in the X* direction such that the cutout 70a engages the latch projection 78. This latches the platform 50, and hence the eject member 53, in its rearward position and maintains the disk cartridge 10 in the disk drive 40. In this manner, the eject latch lever is said to be self-latching.

It is understood that in other embodiments, the eject member 53 may be formed separately from the platform 50 and the platform 50 may be stationary. In such embodiments, the eject member 53 alone will move from the forward position to the rearward position, and the eject latch lever 70 will be adapted to latch the eject member 53 in its rearward position. In still other embodiments, the platform 50 may be omitted. The present invention, as defined by the appended claims, is intended to cover all such embodiments. Figure 8 is a rear end view of the disk drive 40 illustrating the latched position of the eject lever 70. As shown, the eject lever 70 has an elongate, downwardly extending projection 80 that extends downwardly from the lever 70 toward a circuit board 86 mounted on the bottom cover 46 of the disk drive housing. A switch 84 having a plunger 82 is mounted on the circuit board 86. When the platform 50 reaches the rearward position and the cutout 70a engages the latch projection 78, the projection 80 extending from the eject lever 70 will move against the plunger 82 thereby activating the switch 84. A controller (not shown) in the disk drive can sense the activation of the switch 84 and be alerted that the platform 50 has moved into the latched, rearward position. The controller can then initiate rotation of the spindle motor and can signal the solenoid 74 to move the head locking lever 72 and release the linear actuator. As described in co-pending application Serial No. 08/324,671, filed concurrently herewith, entitled "Disk Cartridge and Data Storage Device for Receiving Same" (Attorney Docket IOM-8907) , which is incorporated herein by reference, the disk drive may further comprise apparatus for detecting whether a disk cartridge is indeed present in the disk drive after movement of the platform 50 into its rearward position is detected via switch 84.

Referring now to Figures 9-12, the structure and operation of the solenoid 72 and the first and second movable members (i.e., levers 70, 72) in accordance with the present invention will be described in greater detail. According to the present invention, the single solenoid 74 is adapted to move the first and second members independently in order to selectively perform their respective functions. In the present embodiment, the solenoid is adapted to move the eject latch lever 70 (i.e., first member) and head locking lever 72 (i.e., second member) in order to selectively unlatch the platform 50 and/or unlock the carriage of the head actuator 53. It is understood that the eject latch and head locking levers 70, 72 represent merely one implementation of the present invention. In other embodiments, the first and second movable members may comprise other movable components adapted to perform other disk drive functions. The following discussion of the operation of the eject latch and head locking levers 70, 72 is intended merely to illustrate one exemplary implementation of the present invention in a data storage device and is not intended to be limiting. According to the present invention, each of the movable members (i.e., eject latch and head locking levers 70, 72) has a small projection 70c, 72c positioned in the path of movement of the enlarged end 76a of the solenoid shaft 76. As the drive shaft 76 of the solenoid moves in the X^' direction from its normally extended position (Fig. 9) to its fully retracted position (Fig. 11) , the enlarged end 76a of the drive shaft engages with the respective projections 70c, 72c on the levers 70, 72, moving the levers 70, 72 against the respective biasing forces of the first and second springs 90, 92.

As best shown in Figures 9 and 12, the respective projections 70c, 72c are positioned relative to the enlarged end 76a of the drive shaft 76 such that the end 76a of the drive shaft will contact the projection 72c on the head locking lever 72 (i.e., first movable member) first and will move the head locking lever 72 a predetermined distance to an intermediate position (Fig. 10) of the drive shaft 76 before engaging the projection 70c on the eject lever 70. As such, the head locking lever 70 can be moved independently of the eject lever 70.

According to an important feature of the present invention, the biasing force of the first spring 90 is greater than the biasing force of the second spring 92. Preferably, the biasing force of the first spring is approximately ten (10) times the biasing force of the second spring. As such, the solenoid 74 can be energized with an electrical signal having a first current (e.g., 400 mA) that is sufficient to move the drive shaft 76 of the solenoid 74 against the biasing force of the second spring 92 but is insufficient to move the drive shaft 76 against the biasing force of the first spring 92. As shown in Figure 10, when it is desired to unlock the carriage 62 of the head actuator 60, 96/12279 PC17US95/12985

- 13 - an electrical signal having this first current can be applied to the solenoid 74 causing the drive shaft 76 of the solenoid 74 to move in the X^" direction pulling the head locking lever 72 out of engagement with the end 62a of the actuator carriage 62. However, because the first current is insufficient to overcome the biasing force of the first spring 90, the drive shaft 76 will stop moving when the enlarged end 76a of the drive shaft 76 reaches its intermediate position and contacts the projection 70c on the eject latch lever 70. Thus, in this case, the head locking lever 72 moves to a disengaged position, while the eject lever 70 remains in its latched position. Once the actuator carriage 62 has moved forward and begun its normal operation, the first current can be removed from the solenoid 74 allowing the drive shaft 76 of the solenoid 74 to move back to its extended position (Fig. 9) . At the same time, the second spring 92 will urge the head locking lever 72 back to the position shown in Figure 9.

Like the eject latch lever 70, the head locking lever 72 is self-latching or self-engaging. That is, when the head locking lever 72 is in the position shown in Figure 9 and the rear end 62a of the carriage 62 moves back toward the rear of the disk drive, the rear end 62a will contact an inclined surface 72d at the end 72a of the lever 72. As the carriage 62 moves farther to the rear, the end 62a of the carriage will ride along the inclined surface 72d of the head locking lever 72 causing the head locking lever 72 to move to the side against the bias of spring 92. Once the carriage 62 reaches its full rearward position, the head locking lever 72 will spring back to its engaged position, and the carriage 62 will once again be locked in place, as illustrated in Figure 9. It is desirable to lock the carriage in place whenever the disk drive 40 is not in use, or a disk cartridge has been removed from the disk drive 40. Referring now to Figure 11, when it is desired to eject a disk cartridge from the disk drive, the eject button 52 on the front panel 48 of the disk drive 40 is pushed. A 96/12279 PCI7US95/12985

- 14 - processor (not shown) in the disk drive detects the activation of the eject button and applies an electrical signal to the solenoid 74 having a second, stronger current (e.g., 1.2 Amps) that is sufficient to overcome the combined biasing force of both the springs 90, 92. In this case, the drive shaft 76 of the solenoid 74 moves from its extended position to its fully retracted position. As the drive shaft 76 moves to its fully retracted position, the enlarged operating end 76a of the drive shaft engages the projections 70c, 72c on both levers 70, 72 pulling both levers in the X" direction. This causes the cutout 70a on the eject latch lever 70 to disengage from the latch projection 78, thereby releasing the platform 50 (i.e., eject member 53). Once released, the platform 50 moves back to its forward position under the force of springs 56, 58. As the platform 50 moves back to the forward position, the disk cartridge is backed out of the opening 51 and can then be removed by a user. Immediately after unlatching the platform 50, the second current is removed from the solenoid 74 so that the eject latch lever 70 and head locking lever 72 spring back to the positions shown in Figure 5. The magnitudes of the first and second currents required to overcome the biasing forces of the first and second springs are highly dependent on the characteristics of the particular solenoid employed. The foregoing values are simply exemplary.

As the foregoing illustrate, the present invention provides a means for operating two (or more) movable members in a data storage device to perform two (or more) functions using only a single electro-mechanical device. This capability results from (i) the placement of each movable member relative to the operating end 76a of the drive shaft 76, (ii) the application of different strength biasing forces to each movable member, and (iii) the selective application of electrical signals of different strengths (e.g., currents) to the solenoid. As mentioned above, the present invention may be employed in any data storage device and in any capacity to perform multiple functions in the disk drive using only a single electro-mechanical device.

According to another feature of the present invention, at least a portion of the length of the solenoid drive shaft 76 is cut-away, or reduced in diameter, to provide a channel 76b in which the respective projections 70c, 72c of the first and second movable members (i.e., eject latch and head locking levers 70,72) can move independently of the enlarged operating end 76a of the drive shaft 76. It is this channel 76b that permits movement of the levers 70, 72 during their respective self-latching operations.

Additionally, the channel 76b permits manual operation of the eject latch lever 76b in the event that power to the disk drive 40 or solenoid 74 is interrupted or turned off. When power to the disk drive 40 or solenoid 74 is not available and it is desired to unlatch the platform 50 from its rearward, latched position, a thin rod like instrument, such as a straightened paper clip or the like, can be inserted through a small hole (not shown) in the rear end of the disk drive housing 42. The inserted end of the instrument will contact the inclined surface 70d of the eject latch lever. This will cause the eject latch lever 70 to move to the side until the cutout 70a disengages from the latch projection 78. The platform 50 will therefore spring back to its forward position. All the while, the head locking lever 72 will remain in its engaged position.

Figure 13 is a diagram of an exemplary circuit for applying two different electrical currents, i.e., the first and second currents described above, to an electro-mechanical device, such as the solenoid 74. Q_x is an N-channel MOSFET, and Q₂ is a P-channel MOSFET. _x is the coil of the solenoid 74. Di is a fly-back diode. R_x is a resistor that limits current in the circuit.

To apply a first (i.e., lower) current to the solenoid 74, the gate (G) of Q_x and the gate (G) of Q₂ are both pulled high to Vcc. When the gate of Q₂ is pulled high, Q₂ is turned off and the solenoid current is limited by R_x. To apply a second, greater current to the solenoid 74, the gate of Q_x is pulled high to Vcc, and the gate of Q₂ is pulled low to ground. Q₂ effectively shunts R_x when the gate of Q₂ is pulled to ground. Thus, a greater current is applied to the coil L_x of the solenoid. The solenoid current can be brought to zero by pulling the gate of Q_x to ground, thus turning off Q_{l t}

As the foregoing illustrates, the present invention is directed to a data storage device having apparatus for performing multiple disk drive functions using only a single electro-mechanical device. By achieving these functions using only a single electro-mechanical device, the overall cost and complexity of the disk drive are reduced. The present invention may be employed in any data storage device and is by no means limited to uses described herein. For example, the present invention may be employed in a disk drive that has either a stationary platform, or no platform at all. Additionally, the present invention may be employed in a disk drive that has a rotary actuator as opposed to the linear actuator 60 shown and described herein. Thus, it is understood that changes may be made to the embodiments described above without departing from the broad inventive concepts thereof. Accordingly, the present invention is not limited to the particular embodiments disclosed, but is intended to cover all modifications that are within the spirit and scope of the invention as defined by the appended claims.