1. A ball refiner comprising

The steering mechanism (1) is used for connecting the ball body (10) and providing power for the rotation of the ball body (10);

the grinding mechanism (2) is used for grinding the ball body (10) and is arranged in a staggered manner with the steering mechanism (1);

the grinding device comprises a mounting seat (3), a rotating seat (4) is rotatably arranged on the mounting seat (3), and the grinding mechanism (2) is mounted on the rotating seat (4);

the swinging mechanism (5) is connected with the rotating seat (4) and is used for driving the rotating seat (4) to swing in a reciprocating manner;

it is characterized in that the preparation method is characterized in that,

grind mechanism (2) including the symmetry setting at the grinding subassembly that rotates seat (4) both sides, grinding subassembly includes first power supply (21), first unit head (22) and flexible clamping jaw (23), and flexible clamping jaw (23) link to each other with first power supply (21) through first unit head (22), be equipped with on flexible clamping jaw (23) with disk seat (24) of spheroid (10) laminating are ground through disk seat (24) and spheroid (10) contact.

2. The ball refiner of claim 1, wherein: the flexible clamping jaw (23) comprises

A chuck (231) for clamping the valve seat (24);

the mandrel (232) is connected with the chuck (231) through a connecting disc (233) and drives the chuck (231) to move back and forth;

one end of the push rod (234) is connected to the first power head (22), and the other end of the push rod (234) is connected with the mandrel (232) through a shaft sleeve (235);

an elastic piece (236) is arranged in the shaft sleeve (235), and the elastic piece (236) is pressed between the shaft sleeve (235) and the mandrel (232).

3. The ball refiner of claim 2, wherein: axle sleeve (235) periphery one end shaping has screw thread section (2351), and threaded connection has fixed cover (237) on screw thread section (2351), fixed cover (237) keep away from a pot head of axle sleeve (235) and establish the periphery of dabber (232), and the shaping has spacing retaining ring (2371), dabber (232) one end shaping has spacing boss (2321), and one side of spacing boss (2321) is equipped with elastic component (236).

4. A ball refiner according to claim 2 or 3, characterized in that: be equipped with first installation cavity (2351) and second installation cavity (2352) in axle sleeve (235), be equipped with baffle (2353) between first installation cavity (2351) and second installation cavity (2352), elastic component (236) are located second installation cavity (2352), dabber (232) one end stretches into second installation cavity (2352), just elastic component (236) are pressed and are established between dabber (232) and baffle (2353).

5. The ball refiner of claim 1, wherein: swing mechanism (5) are including fixed setting up second power supply (51) of mount pad (3) one side, and disc (52) are installed to the output of second power supply (51), and disc (52) are gone up the off-centre and are equipped with head rod (53), it is equipped with connecting seat (41) to rotate seat (4) one end, is equipped with second connecting rod (54) through bearing (42) in connecting seat (41), links to each other through connecting rod (55) between head rod (53) and second connecting rod (54).

6. The ball refiner of any one of claims 1-3 or 5, characterized in that: steering mechanism (1) is including setting up fixing base (11) of mount pad (3) both sides are provided with second unit head (12) and third unit head (13) on two fixing base (11) respectively, are equipped with first thimble (14) and second thimble (15) on second unit head (12) and third unit head (13) respectively, press from both sides between first thimble (14) and second thimble (15) and are equipped with dwang (16), and dwang (16) middle part is equipped with through interior bloated anchor clamps (17) spheroid (10).

7. The ball refiner of claim 1, wherein: linear sliding unit is installed to the below of mount pad (3), linear sliding unit is including fixing linear guide (61) on frame (9), and the slidable is provided with slider (62) on linear guide (61), and the upper end of slider (62) is equipped with mount pad (3).

8. The ball refiner of claim 1 or 7, characterized in that: rotate seat (4) through rotating assembly with mount pad (3) link to each other, rotating assembly includes main shaft (71), adapter sleeve (72) and bearing group, main shaft (71) upper end with rotate seat (4) and link to each other, main shaft (71) periphery passes through the bearing group and links to each other with adapter sleeve (72), and adapter sleeve (72) are fixed on mount pad (3).

9. The ball refiner of claim 8, wherein: the bearing group comprises a first bearing (73) and a second bearing (74), and a clamping table (721) for mounting the first bearing (73) and the second bearing (74) is arranged on the inner side of the connecting sleeve (72);

the first bearing (73) comprises an inner ring (731), an outer ring (732) and a plurality of tapered rollers distributed between the inner ring (731) and the outer ring (732), and the top end of the inner ring (731) is higher than that of the outer ring (732); a stop ring (711) is formed at one end, close to the rotating seat (4), of the main shaft (71), the top end of the first inner ring (731) is tightly attached to the stop ring (711), and the bottom end of the outer ring (732) is tightly attached to the top end face of the clamping table (721).

10. The ball refiner of any one of claims 1-3 or 5 or 7, characterized in that: and a material receiving disc (8) is arranged on the rotating seat (4).

Background

In order to meet the sealing performance requirement of the ball valve, the ball body of the ball valve is usually ground.

Like the automatic machine that grinds of spheroid that chinese utility model patent number is CN201720795551.0 discloses, including the steering mechanism that carries out the fixing to the spheroid, drive steering mechanism at the reciprocating swing's of horizontal direction swing mechanism and carry out the bistrique mechanism that grinds to the spheroid, bistrique mechanism and steering mechanism are the staggered arrangement, and vertical track board is connected to swing mechanism, orders about vertical track board around the reciprocal swing of gyration shaft seat for press from both sides the bistrique and can grind spheroidal each different angle.

In the actual working process, because the components such as the steering mechanism, the ball body and the tailstock are arranged on the longitudinal track plate, and because the components are heavier, the running power required by the motor is higher, and the movement of the longitudinal track plate is heavier, so that the processing precision is low, and the device needs to be further improved; meanwhile, the clamping jaws of the grinding head mechanism are in rigid contact, so that the phenomena of workpiece abrasion and the like caused by workpiece collision are easily generated.

Disclosure of Invention

The invention aims to provide a ball refiner, which grinds a ball by driving a grinding mechanism to swing back and forth through a swing mechanism; in addition, the flexible clamping jaw is adopted to clamp the valve seat, so that the valve seat is in flexible contact with a ball body, rigid collision is avoided, and the processing precision is improved.

The purpose of the invention is realized as follows:

a ball refiner comprising

The steering mechanism is used for connecting the ball body and providing power for the rotation of the ball body;

the grinding mechanism is used for grinding the ball body and is arranged in a staggered manner with the steering mechanism;

the mounting seat is rotatably provided with a rotating seat, and the grinding mechanism is mounted on the rotating seat;

the swinging mechanism is connected with the rotating seat and is used for driving the rotating seat to swing back and forth;

grind mechanism including the symmetry setting at the grinding component who rotates the seat both sides, grinding component includes first power supply, first unit head and flexible clamping jaw, and flexible clamping jaw passes through first unit head and links to each other with first power supply, be equipped with on the flexible clamping jaw with the disk seat of spheroid laminating grinds through disk seat and spheroid contact.

It is further provided that the flexible jaw comprises

A chuck for clamping the valve seat;

the mandrel is connected with the chuck through a connecting disc and drives the chuck to move back and forth;

one end of the push rod is connected to the first power head, and the other end of the push rod is connected with the mandrel through a shaft sleeve;

the shaft sleeve is internally provided with an elastic piece, and the elastic piece is pressed between the shaft sleeve and the mandrel.

Further set up as, axle sleeve periphery one end shaping has the screw thread section, and threaded connection has fixed cover on the screw thread section, the fixed pot of keeping away from the axle sleeve is established the periphery of dabber, and the shaping has spacing retaining ring, dabber one end shaping has spacing boss, and one side of spacing boss is equipped with the elastic component.

Further set up as, be equipped with first installation cavity and second installation cavity in the axle sleeve, be equipped with the baffle between first installation cavity and the second installation cavity, the elastic component is located the second installation cavity, dabber one end stretches into the second installation cavity, just the elastic component is pressed and is established between dabber and the baffle.

The swing mechanism comprises a second power source fixedly arranged on one side of the mounting seat, a disc is installed at the output end of the second power source, a first connecting rod is eccentrically arranged on the disc, a connecting seat is arranged at one end of the rotating seat, a second connecting rod is arranged in the connecting seat through a bearing, and the first connecting rod is connected with the second connecting rod through a connecting rod.

Further set up as, steering mechanism is including setting up the fixing base of mount pad both sides is provided with second unit head and third unit head on two fixing bases respectively, is equipped with first thimble and second thimble on second unit head and the third unit head respectively, presss from both sides between first thimble and the second thimble and is equipped with the dwang, and the dwang middle part is equipped with through the interior anchor clamps that expand the spheroid.

Further, a linear sliding unit is installed below the installation seat and comprises a linear guide rail fixed on the machine base, a sliding block is slidably arranged on the linear guide rail, and the installation seat is arranged at the upper end of the sliding block.

The rotating seat is connected with the mounting seat through a rotating assembly, the rotating assembly comprises a main shaft, a connecting sleeve and a bearing group, the upper end of the main shaft is connected with the rotating seat, the periphery of the main shaft is connected with the connecting sleeve through the bearing group, and the connecting sleeve is fixed on the mounting seat.

The bearing set comprises a first bearing and a second bearing, and a clamping table for mounting the first bearing and the second bearing is arranged on the inner side of the connecting sleeve;

the first bearing comprises an inner ring, an outer ring and a plurality of tapered rollers distributed between the inner ring and the outer ring, and the top end of the inner ring is higher than the top end of the outer ring; and a retaining ring is formed at one end of the main shaft close to the rotating seat, the top end of the first inner ring is tightly attached to the retaining ring, and the bottom end of the outer ring is tightly attached to the top end face of the clamping table.

Further, a material receiving disc is arranged on the rotating seat.

Compared with the prior art, the invention has the outstanding and beneficial technical effects that:

1. the grinding mechanism provided by the invention adopts a mode that the first power source drives the flexible clamping jaw to move the valve seat to be matched with the ball body for grinding, and in the whole process that the flexible clamping jaw is driven to move, when the clamped valve seat is contacted with the ball body, resistance can be applied, the flexible clamping jaw can move backwards, abrasion caused by hard collision between the valve seat and the ball body is avoided, rigid touch is converted into flexible touch, and the service life of a workpiece is prolonged.

2. The swinging mechanism is connected with the grinding mechanism and used for driving the grinding mechanism to swing back and forth in the machining process, so that the grinding mechanism can grind different angles on the surface of a sphere, and the uniform and automatic grinding of the whole sphere is realized.

3. The swing mechanism adopts a second power source to drive the connecting rod to eccentrically rotate so as to drive the rotating seat to swing, the connecting mode between the connecting rod and the rotating seat adopts the connecting mode between the bearing and the second connecting rod, on one hand, the bearing has better bearing capacity, on the other hand, the rotating seat is smooth in reciprocating swing, phenomena of blocking and the like do not occur, the processing effect is ensured, the processing precision can be improved, and the product scrapping is avoided.

4. The clamping mechanism, the grinding mechanism and the steering mechanism are directly driven by the power head, and the device is simple in structure and good in driving effect.

5. The rotating seat is connected with the mounting seat through the rotating assembly, the rotating assembly comprises a first bearing and a second bearing, the first bearing is a tapered roller bearing, the tapered roller bearing has better load capacity, and the load capacity of the second bearing is added, so that the load capacity of the whole rotating seat is obviously and greatly improved, and the rotating seat is prevented from being damaged due to long-time use.

6. According to the invention, the receiving disc is arranged on the rotating seat and is positioned below the ball body, so that the receiving disc can receive the scraps generated in the ball body grinding process and the falling grinding paste, the centralized treatment or recovery is convenient, and the scraps are prevented from falling all around.

Drawings

Fig. 1 is a schematic perspective view of the present invention.

FIG. 2 is a schematic view of a polishing assembly according to the present invention.

Figure 3 is a schematic diagram of the construction of the flexible jaw of the present invention.

Figure 4 is a cross-sectional view of a flexible jaw of the present invention.

Figure 5 is an exploded view of the structure of the flexible jaw of the present invention.

Figure 6 is a cross-sectional view of an abrasive assembly of the present invention.

Fig. 7 is a schematic view of the installation structure of the swing mechanism of the present invention.

Fig. 8 is a schematic perspective view of the swing mechanism of the present invention.

Fig. 9 is a schematic top view of the swing mechanism of the present invention.

Fig. 10 is a schematic sectional view of the structure at a-a in fig. 9.

Fig. 11 is a schematic sectional view of the structure at B-B in fig. 9.

Fig. 12 is a partially enlarged view of fig. 10 at C.

Fig. 13 is a partial enlarged view of fig. 10 at D.

Fig. 14 is a partial enlarged view of fig. 11 at E.

Fig. 15 is a schematic view of a link mounting structure of the swing mechanism of the present invention.

FIG. 16 is a schematic view of the polishing mechanism of the present invention.

Fig. 17 is a schematic view of the mounting structure of the mounting base of the present invention.

FIG. 18 is a schematic sectional view of the grinding mechanism of the present invention.

Reference numerals: 1-a steering mechanism; 11-a fixed seat; 12-a second powerhead; 13-a third power head; 14-a first thimble; 15-a second thimble; 16-rotating rods; 17-an internal expansion clamp; 2-a grinding mechanism; 21-a first power source; 22-a first powerhead; 23-a flexible jaw; 231-a chuck; 232-mandrel; 233-connecting disc; 234-a push rod; 235-shaft sleeve; 236-an elastic member; 24-a valve seat; 3-mounting a base; 4-rotating the base; 41-a connecting seat; 42-a bearing; 5-a swing mechanism; 51-a second power source; 52-disc; 53-first connecting rod; 54-a second connecting rod; 55-a connecting rod; 61-linear guide; 62-a slide block; 71-a main shaft; 711-stop collar; 72-connecting sleeve; 721-cassette; 73-a first bearing; 731-inner ring; 732-an outer ring; 74-a second bearing; 8-a take-up pan; 9-a frame; 91-a stand; 10-sphere.

Detailed Description

The following description of the embodiments of the present invention will be made in detail with reference to the accompanying drawings, which are shown in fig. 1 to 18.

As shown in fig. 1, a ball refiner comprises a frame 9, a base 91 is arranged on the top of the frame, a steering mechanism 1 for fixing and rotating a ball 10, a grinding mechanism 2 for grinding the ball 10 and a swing mechanism 5 are mounted on the base 91, and the grinding mechanism 2 and the steering mechanism 1 are arranged in a staggered manner. The machine base 9 is movably provided with a mounting seat 3, the mounting seat 3 is rotatably provided with a rotating seat 4, and the grinding mechanism 2 is arranged on the rotating seat 4; the swing mechanism 5 is connected with the rotating seat 4 and used for driving the rotating seat 4 to swing in a reciprocating manner.

Grinding mechanism:

grind mechanism 2 including the symmetry set up the grinding component in the seat of rotating 4 both sides, grinding component includes first power supply 21, first unit head 22 and flexible clamping jaw 23, as shown in fig. 2, flexible clamping jaw 23 links to each other with first power supply 21 through first unit head 22, be equipped with on the flexible clamping jaw 23 with the disk seat 24 of spheroid 10 laminating grinds through disk seat 24 and spheroid 10 contact.

As shown in fig. 3-5, the flexible clamping jaw 23 comprises a chuck 231, a mandrel 232 and a sleeve 235, the chuck 231 is used for clamping a workpiece, the mandrel 232 is connected with the chuck 231 through a connecting disc 233, and the sleeve 235 is used for connecting to a power source; the elastic member 236 is disposed in the sleeve 235, and the elastic member 236 is pressed between the sleeve 235 and the core 232. The elastic member 236 is a spring, and when the clamped workpiece contacts another workpiece or object during the entire process of driving the flexible clamping jaw to move, if the workpiece is subjected to resistance, the spring will generate a certain elastic force, so as to avoid abrasion caused by hard collision between the workpiece and another workpiece or object. The rigid touch is changed into flexible touch, and the service life of the workpiece is prolonged.

Axle sleeve 235 periphery one end shaping has screw thread section 2351, and threaded connection has fixed cover 237 on the screw thread section 2351, fixed cover 237 is kept away from an pot head of axle sleeve 235 and is established the periphery of dabber 232, and the shaping has spacing retaining ring 2371, dabber 232 one end shaping has spacing boss 2321, and one side of spacing boss 2321 is equipped with elastic component 236. The movement of the limiting boss is limited by the matching of the limiting boss and the limiting check ring, and the separation of the limiting boss and the limiting check ring caused by excessive movement is avoided.

One end surface of the connecting disc 233 is recessed inwards to form a mounting groove 2331, a connecting hole 2332 and a counter bore 2333 which are respectively connected with the chuck 231 and the mandrel 232 are formed in the mounting groove 2331, and a mounting boss 2311 embedded into the mounting groove 2331 is formed on one side of the chuck 231. The cooperation of installation boss 2311 and mounting groove makes the chuck inseparabler with being connected between the connection pad, and simultaneously, the design of counter bore makes the connection pad can not bulge with being connected of dabber, and influences being connected of connection pad and chuck.

The chuck 231 is a three-jaw chuck and comprises a chuck body 2312, the mounting boss 2311 is formed on one side of the chuck body 2312 in a molding mode, three clamping grooves 2313 are circumferentially and uniformly arranged on the other side of the chuck body 2312, a clamping jaw 2314 is installed in each clamping groove 2313, clamping tables 2315 are formed at the outer ends of the clamping jaws 2314, and an area 2316 for clamping a workpiece is formed among the three clamping tables 2315.

A first mounting cavity 2354 and a second mounting cavity 2352 are arranged in the shaft sleeve 235, a partition 2353 is arranged between the first mounting cavity 2354 and the second mounting cavity 2352, the elastic part 236 is positioned in the second mounting cavity 2352, one end of the mandrel 232 extends into the second mounting cavity 2352, and the elastic part 236 is pressed between the mandrel 232 and the partition 2353. First mounting cavity 2354 is used for mounting a push rod 234 of a power source to facilitate coupling of the power source to the flexible jaw to drive the flexible jaw into operation.

The mandrel 232 and the shaft sleeve 235 are arranged in a hollow mode, materials are saved, and the structure is light.

The first power source 21 is a motor, as shown in fig. 6, a push rod 221 is disposed in the first power head 22, an outer end of the push rod 221 extends out of the first power head 22 and is connected to the shaft sleeve 235, and an inner end of the push rod 221 is connected to an output shaft of the motor through a belt transmission device.

The first power head 22 comprises a housing 222 and a pushing assembly, wherein a core bar 223 is arranged in the housing 222, the pushing assembly comprises a guide rod 224 arranged outside the housing 222, a driving cylinder 225 and a sliding block 226 movably arranged on the guide rod 224, one end of the sliding block 226 extends into the housing 222 to be connected with the core bar 223, and the push rod 221 is arranged in the core bar 223. The housing 222 defines an opening 227 into which the slider 226 extends. When the driving cylinder 225 drives the sliding block 226 to move on the guide rod 224, the driving cylinder can drive the guide rod 224 to move, so as to push the flexible clamping jaw to move.

A swinging mechanism:

as shown in fig. 7, the swing mechanism 5 includes a second power source 51 fixedly disposed on one side of the mounting base 3, a disc 52 is mounted at an output end of the second power source 51, a first connecting rod 53 is eccentrically disposed on the disc 52, a connecting base 41 is disposed at one end of the rotating base 4 close to the second power source 51, a second connecting rod 54 is disposed in the connecting base 41 through a bearing 42, and the first connecting rod 53 is connected to the second connecting rod 54 through a connecting rod 55. As shown in fig. 8-12, the disc 52 is eccentrically provided with the first connecting rod 53, the bearing 42 is internally provided with the second connecting rod 54 in an inner ring, and two ends of the connecting rod 55 are respectively connected with the first connecting rod 53 and the second connecting rod 54. The second power source 51 is a motor, the output end of the motor is connected with the disc 52 through a speed reducer 511, the disc 52 is driven to rotate by the motor, and the first connecting rod 53 is eccentrically arranged on the disc 52, so that the rotating base 4 is pulled by the connecting rod 55 to swing back and forth. The second connecting rod 54 is installed on the connecting seat 41 through the bearing 42, and the bearing 42 rolls smoothly, so that the connecting rod can swing smoothly when the rotating seat is pulled, and the phenomenon that the ball is ground by a subsequent refiner due to blockage caused by direction adjustment is avoided.

A connector 56 is arranged at one end of the connecting rod 55 connected with the first connecting rod 53, and a first through hole for the first connecting rod 53 to pass through is formed in the connector 56; the lower end of the second connecting rod 54 extends into the inner ring of the bearing 51, the upper end of the second connecting rod extends out of the connecting seat 41 and is provided with a second through hole, and the connecting rod 55 penetrates through the second through hole. As shown in fig. 13 and 15, a clamping groove 521 having an opening extending to the edge of the disc 52 is formed in the disc 52, a connecting block 522 is clamped in the clamping groove 521, the first connecting rod 53 is inserted into the connecting block 522, the opening of the clamping groove 521 is directly connected to the edge, and the connecting block 522 is conveniently embedded in the clamping groove 521 for installation.

The rotating seat 4 is connected with the mounting seat 3 through a rotating assembly, the rotating assembly comprises a main shaft 71, a connecting sleeve 72 and a bearing set, the upper end of the main shaft 71 is connected with the rotating seat 4, the periphery of the main shaft 71 is connected with the connecting sleeve 72 through the bearing set, and the connecting sleeve 72 is fixed on the mounting seat 3. The bearing set comprises a first bearing 73 and a second bearing 74, and a clamping platform 721 for mounting the first bearing 73 and the second bearing 74 is arranged inside the connecting sleeve 72.

As shown in fig. 11 and 14, the first bearing 73 is a tapered roller bearing, and includes an inner ring 731, an outer ring 732, and a plurality of tapered rollers distributed between the inner ring 731 and the outer ring 732, wherein a top end of the inner ring 731 is disposed higher than a top end of the outer ring 732; a stop ring 711 is formed at one end of the main shaft 71 close to the rotating seat 4, the top end of the first inner ring 731 is tightly attached to the stop ring 711, and the bottom end of the outer ring 732 is tightly attached to the top end surface of the clamping platform 721. In the in-service use, need the heavier grinding mechanism of installation quality on rotating the seat, have great requirement to the bearing capacity and the smooth degree of rotation that rotate the seat, consequently, adopt the structure of duplex bearing to set up rotating assembly, not only have better bearing capacity, still possess smooth pivoted advantage.

The rotating seat 4 is provided with a receiving disc 8 for receiving scraps and grinding paste generated in the grinding process of the ball body, so that the ball body is convenient to recover and treat.

A steering mechanism:

as shown in fig. 16, the steering mechanism 1 includes fixing seats 11 disposed on two sides of the mounting seat 3, a second power head 12 and a third power head 13 are respectively disposed on the two fixing seats 11, a first thimble 14 and a second thimble 15 are respectively disposed on the second power head 12 and the third power head 13, a rotating rod 16 is sandwiched between the first thimble 14 and the second thimble 15, and the ball 10 is disposed in the middle of the rotating rod 16 through an internal expansion fixture 17.

As shown in fig. 18, one end of the second power head 12 is connected to the motor 18 through a belt transmission mechanism, and operates under the driving of the motor 18, the second power head 12 includes a housing 121, a rotating shaft 122 is disposed in the housing, one end of the rotating shaft is connected to the belt transmission mechanism, the other end of the rotating shaft extends out of the housing 121 to be connected to the first thimble 14, and the rotating shaft 122 drives the first thimble 14 to rotate under the driving of the motor 18, so as to drive the rotating rod 16 to rotate.

As shown in fig. 17, a linear sliding unit is mounted below the mounting seat 3, the linear sliding unit includes a linear guide rail 61 fixed on a base 91, a sliding block 62 is slidably disposed on the linear guide rail 61, and the mounting seat 3 is disposed at an upper end of the sliding block 62.

The working principle of the invention is as follows:

firstly, a linear sliding unit is adjusted, the position of a mounting seat is fixed, then a ball to be ground is mounted between a first thimble and a second thimble through a rotating rod, the ball is located above a receiving disc, then a valve seat matched with the corresponding ball is mounted to a grinding mechanism through a flexible clamping jaw, as shown in figure 1, valve seats are arranged on two sides of the ball, the mounting of the ball is completed, and grinding paste is brushed on the surface of the ball.

When the ball grinding machine works, the rotating mechanism drives the ball body to rotate, the swinging mechanism drives the rotating seat and the grinding mechanism on the rotating seat to swing in a small left-right range, and the ball body is ground through continuous contact between the valve seat and the ball body in the rotating and swinging processes of the ball body and the valve seat.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.