1. A rapid positioning and clamping device for long hole shaft multi-boss parts is characterized by comprising an axial positioning device, a radial horizontal supporting and clamping device and a clamp bottom plate (8),

the axial positioning device comprises a left end positioning mechanism (1) and a right end positioning mechanism (2), wherein the left end positioning mechanism (1) and the right end positioning mechanism (2) are respectively fixed at two ends of a clamp bottom plate (8), are positioned on a straight line and distributed oppositely, and respectively support and position holes at two ends of the long hole shaft type multi-boss part;

the radial positioning device comprises a support end (3) and a compression end (4), the support end (3) and the compression end (4) are respectively positioned at two radial sides of the long-hole shaft multi-boss part and are fixed on a clamp bottom plate (8), the support end (3) provides support force for one side of the long-hole shaft multi-boss part, and the compression end (4) is provided with a telescopic compression pin (25) and can be switched between two states of compressing the multi-boss part or not;

radial horizontal support and clamping device are including radial horizontal strutting arrangement (5) and to horizontal clamping device (6) that are located many boss part both sides of slot hole axle type, radial horizontal strutting arrangement (5) are located many boss part both sides of slot hole axle type respectively with to horizontal clamping device (6) and just adorn on anchor clamps bottom plate (8), and both have the clamp plate and can drive the mechanism that the clamp plate removed to the centre, realize the clamp of many boss parts of slot hole axle type.

2. The device for rapidly positioning and clamping the long-hole shaft multi-boss machining part as claimed in claim 1, wherein the number of the radial horizontal supporting and clamping devices is multiple.

3. The device for rapidly positioning and clamping the long-hole shaft type multi-boss machining part according to claim 1, wherein the left end positioning mechanism (1) comprises a left support (10), a split pin (12), a left end cover (13), a spring (14), a left bushing (15) and a left live center (16), the left support (10) is fixed at one end of the clamp bottom plate (8), and the left bushing (15) is fixed in the left support (10) and cannot move; the rear end of the left live center (16) is provided with a rod part, the rod part is sleeved with a spring (14), the left live center (16) and the spring (14) are positioned in a space enclosed by the left bushing (15) and the left end cover (13), the rod part of the left live center (16) penetrates through the left end cover (13), the tail part of the left live center penetrates through a split pin (12), and the left live center (16) can freely slide in the left bushing (15);

the right end positioning mechanism (2) comprises a right support (19), a right end cover (21), a right bushing (18), a right live center (17) and a handle (22), the right support (19) is fixed at the other end of the clamp bottom plate (8), and the right bushing (18) is fixed in the right support (19) and cannot move; the rear end of the right live center (17) is provided with a counter bore, the right live center (17) is positioned in a space enclosed by the right bushing (18) and the right end cover (21), the rod part of the handle (22) penetrates through the right end cover (21) to be matched with the counter bore, and the handle (22) is rotated left and right to drive the right live center (17) to freely slide in the right bushing (18).

4. The device for rapidly positioning and clamping the long-hole shaft type multi-boss processing part as claimed in claim 1, wherein the supporting end (3) comprises a supporting nail (24) and a supporting nail seat (22), and the pressing end (4) comprises a pressing nail (25), a pressing nail seat (27), a spring (26), a hook-shaped block (28) and a first nut (29); a supporting nail seat (22) and a pressing nail seat (27) are respectively arranged at two radial sides of the long-hole shaft multi-boss part and are fixed on the clamp bottom plate (8), and a supporting nail (24) is fixed on the supporting nail seat (22) to form a supporting end (3); the pressing nail (25) is arranged on the pressing nail seat (27), the pressing nail (25) is sleeved with a spring (26) located inside the pressing nail seat (27), the end part of the pressing nail (25) extends out of the pressing nail seat (27), the hook-shaped block (28) is arranged on the pressing nail (25), the nut (29) is in threaded connection with the pressing nail (25), and the hook-shaped block (28) is located between the nut (29) and the pressing nail seat (27).

5. The device for rapidly positioning and clamping the long-hole shaft multi-boss processing part as claimed in claim 1, wherein the radial horizontal supporting and clamping device comprises a clamp body (32), a supporting bolt (31), a pressing bolt (38), a pressing plate, a fixing plate (33), a set screw (35) and a second nut (36); the number of the clamp bodies (32) is two, the two clamp bodies are respectively arranged on two sides of a long hole shaft type multi-boss part and fixed on the clamp bottom plate (8) through bolts (30), a plurality of horizontal screw holes are formed in the two clamp bodies (32), a supporting bolt (31) is screwed in the horizontal screw hole of one clamp body (32), a pressing bolt (38) is screwed in the horizontal screw hole of the other clamp body (32), pressing plates are arranged at the heads of the supporting bolt (31) and the pressing bolt (38), the supporting bolt (31), the pressing bolt (38) and a pressing plate support are connected in a floating mode through fixing plates (33), second nuts (36) and bolts (34).

6. The device for rapidly positioning and clamping the long-hole shaft multi-boss processing parts as claimed in claim 5, wherein the floating connection mode is as follows: a gap is reserved between the pressing plate and the fixing plate (33), the pressing plate and the fixing plate are connected through a bolt (34), a through hole is formed in the fixing plate (33), the supporting bolt (31) or the pressing bolt (38) penetrates through the through hole of the fixing plate (33), and a nut seat is assembled at the end of the supporting bolt or the pressing bolt.

7. The device for rapidly positioning and clamping the long-hole shaft type multi-boss processing part according to claim 5 or 6, wherein the pressing plate is a V-shaped pressing plate (37), and a V-shaped groove is formed in the end face of the V-shaped pressing plate (37); or the pressing plate is an arc-shaped pressing plate, and an arc-shaped recess is formed in the end face of the arc-shaped pressing plate.

8. The device for rapidly positioning and clamping the long-hole shaft multi-boss machining part as claimed in claim 1, further comprising a radial vertical auxiliary supporting device (7); the radial vertical auxiliary supporting device (7) is arranged on the clamp bottom plate (8) and positioned at the lower part of the long hole shaft type multi-boss part and is provided with a device with the top surface height adjustable so as to realize vertical auxiliary supporting of the long hole shaft type multi-boss part.

9. The device for rapidly positioning and clamping the long-hole shaft multi-boss machining part as claimed in claim 8, wherein the number of the radial vertical auxiliary supporting devices (7) is multiple.

10. The device for rapidly positioning and clamping the long-hole shaft multi-boss machining part as claimed in claim 8, wherein the radial vertical auxiliary supporting device comprises a wedge (41), a wedge guide rail (39) and an adjusting screw (42); the inclined iron guide rail (39) is fixed on the clamp bottom plate (8); the axis of the wedge guide rail (39) is vertical to the axis of the long hole shaft multi-boss part, the wedge (41) is arranged in the wedge guide rail (39), the adjusting screw (42) horizontally penetrates through the clamp body (32), and the tail part of the adjusting screw is contacted with the large end of the wedge (41).

Background

The long hole shaft type multi-boss part is provided with a plurality of bosses to be processed, and the bosses have higher related technical requirements with holes at two ends besides the requirement of mutual position tolerance. The hydraulic positioning and clamping mode can be adopted for parts with larger batches, and the manual positioning and clamping mode is suitable for parts with small batches in consideration of cost factors.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a manual rapid positioning and clamping method which is used for machining bosses after rapidly positioning and clamping multiple boss parts of a long hole shaft.

The present invention achieves the above-described object by the following technical means.

A rapid positioning and clamping device for long hole shaft multi-boss parts is characterized by comprising an axial positioning device, a radial horizontal supporting and clamping device and a clamp bottom plate,

the axial positioning device comprises a left end positioning mechanism and a right end positioning mechanism, the left end positioning mechanism and the right end positioning mechanism are respectively fixed at two ends of the clamp bottom plate, are positioned on a straight line and distributed oppositely, and respectively support and position holes at two ends of the long hole shaft type multi-boss part;

the radial positioning device comprises a support end and a pressing end, wherein the support end and the pressing end are respectively positioned at two radial sides of the long-hole shaft multi-boss part and are fixed on the clamp bottom plate, the support end provides support force for one side of the long-hole shaft multi-boss part, and the pressing end is provided with a telescopic pressing nail and can be switched between two states of pressing or not pressing the multi-boss part;

the radial horizontal supporting and clamping device comprises a radial horizontal supporting device and a radial horizontal clamping device, wherein the radial horizontal supporting device and the radial horizontal clamping device are positioned on two sides of the multiple boss parts of the long hole shaft, are respectively positioned on two sides of the multiple boss parts of the long hole shaft and are arranged on the clamp bottom plate, and the radial horizontal supporting device and the radial horizontal clamping device are respectively provided with a pressing plate and a mechanism capable of driving the pressing plate to move towards the middle, so that the clamping of the multiple boss parts of the long hole shaft is realized.

Further, the number of the radial horizontal supporting and clamping devices is multiple.

Furthermore, the left end positioning mechanism comprises a left support, a cotter pin, a left end cover, a spring, a left bushing and a left live center, the left support is fixed at one end of the clamp bottom plate, and the left bushing is fixed in the left support and cannot move; the rear end of the left live center is provided with a rod part, the rod part is sleeved with a spring, the left live center and the spring are positioned in a space enclosed by the left bushing and the left end cover, the rod part of the left live center penetrates through the left end cover, the tail part of the left live center penetrates through a cotter pin, and the left live center can freely slide in the left bushing;

the right end positioning mechanism comprises a right support, a right end cover, a right bushing, a right live center and a handle, the right support is fixed at the other end of the clamp bottom plate, and the right bushing is fixed in the right support and cannot move; the rear end of the right live center is provided with a counter bore, the right live center is positioned in a space enclosed by the right bushing and the right end cover, the rod part of the handle penetrates through the right end cover to be matched with the counter bore, and the right live center can be driven to freely slide in the right bushing by rotating the handle left and right.

Further, the supporting end comprises a supporting nail and a supporting nail seat, and the pressing end comprises a pressing nail, a pressing nail seat, a spring, a hook-shaped block and a first nut; the supporting nail seat and the pressing nail seat are respectively arranged at two radial sides of the long-hole shaft multi-boss part and are fixed on the clamp bottom plate, and the supporting nail is fixed on the supporting nail seat to form a supporting end; the compression nail is arranged on the compression nail seat, the compression nail is sleeved with a spring positioned in the compression nail seat, the end part of the compression nail extends out of the compression nail seat, the hook-shaped block is arranged on the compression nail, the nut is in threaded connection with the compression nail, and the hook-shaped block is positioned between the nut and the compression nail seat.

Further, the radial horizontal supporting and clamping device comprises a clamp body, a supporting bolt, a pressing plate, a fixing plate, a set screw and a second nut; the number of the clamp bodies is two, the two clamp bodies are respectively arranged on two sides of the long hole shaft type multi-boss part and are fixed on the clamp bottom plate through bolts, the two clamp bodies are respectively provided with a plurality of horizontal screw holes, a supporting bolt is screwed into the horizontal screw hole of one clamp body, a compression bolt is screwed into the horizontal screw hole of the other clamp body, the heads of the supporting bolt and the compression bolt are respectively provided with a pressure plate, and the supporting bolt, the compression bolt and a pressure plate support are connected in a floating mode through a fixing plate, a second nut and bolts.

Further, the floating coupling is realized by the following steps: a gap is reserved between the pressing plate and the fixing plate, the pressing plate and the fixing plate are connected through a bolt, a through hole is formed in the fixing plate, the supporting bolt or the pressing bolt penetrates through the through hole of the fixing plate, and a nut seat is assembled at the end of the supporting bolt or the pressing bolt.

Furthermore, the pressing plate is a V-shaped pressing plate, and a V-shaped groove is formed in the end face of the V-shaped pressing plate; or the pressing plate is an arc-shaped pressing plate, and an arc-shaped recess is formed in the end face of the arc-shaped pressing plate.

Further, the device also comprises a radial vertical auxiliary supporting device; the radial vertical auxiliary supporting device is arranged on the clamp bottom plate and positioned at the lower part of the long hole shaft type multi-boss part and is provided with a device with the height of the top surface adjustable, so that vertical auxiliary supporting for the long hole shaft type multi-boss part is realized.

Further, the number of the radial vertical auxiliary supporting devices is multiple.

Further, the radial vertical auxiliary supporting device comprises an inclined iron, an inclined iron guide rail and an adjusting screw; the inclined iron guide rail is fixed on the clamp bottom plate; the axis of the wedge guide rail is perpendicular to the axis of the long hole shaft type multi-boss part, the wedge is arranged in the wedge guide rail, the adjusting screw horizontally penetrates through the clamp body, and the tail part of the wedge is contacted with the big end of the wedge.

The invention has the beneficial effects that:

1. the clamp designed and manufactured according to the method of the invention has simple structure, convenient operation and reliable positioning and clamping.

2. The clamp designed according to the method of the invention has lower manufacturing cost and is very suitable for processing parts in medium and small batches.

3. On the basis of the method, the hydraulic station, the hydraulic supporting cylinder and the hydraulic clamping cylinder are added, so that hydraulic clamping can be realized, seamless switching from medium and small batch production to mass production is realized, and the period of secondary design and manufacturing of the processing clamp is greatly shortened.

Drawings

Fig. 1 is a schematic structural diagram of a rapid positioning and clamping device for long-hole shaft multi-boss parts according to the invention.

Fig. 2 is a schematic structural diagram of the long hole shaft type multi-boss part needing to be clamped in positioning and clamping.

Fig. 3 is a schematic structural view of the axial positioning device.

Fig. 4 is a schematic structural diagram of a radial positioning device.

Fig. 5 is a schematic view of the radial horizontal supporting and clamping device.

Fig. 6 is a schematic structural view of a radial vertical auxiliary supporting device.

Wherein:

1. a left end positioning mechanism; 2. a right end positioning mechanism; 3. a support end, 4. a pressing end; 5, radial horizontal support; 6. a radial clamping device; 7. radial vertical auxiliary supporting devices; 8. a clamp base plate; 9. a first screw; 11. a second screw; 20. a third screw; 10. a left support; 12. a cotter pin; 13. a left end cap; 14. a spring; 15. a left bushing; 16. a left live center; 17. a right live center; 18. a right bushing; 19. a right support; 21. a right end cap; 22. a handle; 22. a support nail seat; 23. a fourth screw; 24. a support pin; 25. pressing nails; 26. a spring; 27. pressing the nail seat; 28. a hook block; 29. a first nut; 30. a bolt; 31. a support bolt; 32. a clamp body; 33. a fixing plate; 35. tightening the screw; 36. a second nut; a V-shaped platen; 38. a hold-down bolt; 39. a wedge guide rail; 40. a fifth screw; 41. a wedge; 42. and adjusting the screw.

Detailed Description

The invention will be further described with reference to the following figures and specific examples, but the scope of the invention is not limited thereto.

Fig. 1 and fig. 3 are schematic diagrams of a device for rapidly positioning and clamping multiple boss parts of a long hole shaft according to the invention. The fixture is arranged on a workbench of a machine tool of a machining center and comprises an axial positioning device, a radial horizontal supporting and clamping device, a radial vertical auxiliary supporting device 7 and a fixture bottom plate 8.

The axial positioning device comprises a left end positioning mechanism 1 and a right end positioning mechanism 2, wherein the left end positioning mechanism 1 and the right end positioning mechanism 2 are respectively positioned at two ends of the clamp bottom plate 8 and are positioned on a straight line and distributed oppositely, so that the left live center 16 and the right live center 17 are coaxial.

The left end positioning mechanism 1 comprises a left support 10, a cotter pin 12, a left end cover 13, a spring 14, a left bush 15 and a left live center 16, wherein the left support 10 is fixed at one end of the clamp bottom plate 8 through 4 first screws 9, and the left bush 15 is fixed in the left support 10 and cannot move; the rear end of the left live center 16 is provided with a rod part, the rod part is sleeved with a spring 14, the left live center 16 and the spring 14 are located in a space enclosed by a left bushing 15 and a left end cover 13, the left end cover 13 is fixed at the end part of the left bushing 15 through a second screw, the rod part of the left live center 16 penetrates through the left end cover 13, the tail part of the left live center penetrates through a cotter pin 12, and the left live center 16 can freely slide in the left bushing 15.

The right end positioning mechanism 2 comprises a right support 19, a right end cover 21, a right bushing 18, a right live center 17 and a handle 22, the right support 19 is fixed at the other end of the clamp bottom plate 8 through 4 first screws 9, and the right bushing 18 is fixed in the right support 19 and cannot move; the rear end of the right live center 17 is provided with a counter bore, the right live center 17 is positioned in a space enclosed by the right bushing 18 and the right end cover 21, the right end cover 21 is fixed at the end part of the right bushing 18 through a third screw, the rod part of the handle 22 penetrates through the right end cover 21 to be matched with the counter bore, and the handle 22 is rotated left and right to drive the right live center 17 to freely slide in the right bushing 18.

The radial positioning device is composed of a support end 3 and a pressing end 4, wherein the support end 3 comprises a support nail 24 and a support nail seat 22, and the pressing end 4 comprises a pressing nail 25, a pressing nail seat 27, a spring 26, a hook block 28 and a first nut 29; the supporting nail seat 22 and the pressing nail seat 27 are respectively arranged at two radial sides of the long-hole shaft multi-boss part and are fixed on the clamp bottom plate 8 through a fourth screw 23, and the supporting nail 24 is fixed on the supporting nail seat 22 to form a supporting end 3; the pressing nail 25 is arranged on the pressing nail seat 27, the pressing nail 25 is sleeved with a spring 26 positioned in the pressing nail seat 27, the end part of the pressing nail 25 extends out of the pressing nail seat 27, the hook-shaped block 28 is arranged on the pressing nail 25, the nut 29 is in threaded connection with the pressing nail 25, and the hook-shaped block 28 is positioned between the nut 29 and the pressing nail seat 27. The heads of the support pins 24 and the hold-down pins 25 are arranged in line opposite to each other. The rod part of the pressing nail 25 is sleeved with a spring 26, the hook block 28 is rotated to drive the pressing nail 25 to move back and forth to realize pressing and loosening, and the pressing force is adjusted by selecting springs 26 with different diameters and turns.

The radial horizontal supporting and clamping device comprises a clamp body 32, a supporting bolt 31, a pressing bolt 38, a V-shaped pressing plate 37, a fixing plate 33, a set screw 35 and a second nut 36. The number of the clamp bodies 32 is 2, the clamp bodies are respectively arranged on two sides of a long-hole shaft type multi-boss part and are fixed on the clamp bottom plate 8 through bolts 30, a plurality of horizontal screw holes are formed in each of the 2 clamp bodies 32, a supporting bolt 31 is screwed into the horizontal screw hole of one clamp body 32, a pressing bolt 38 is screwed into the horizontal screw hole of the other clamp body 32, V-shaped pressing plates 37 are arranged at the heads of the supporting bolt 31 and the pressing bolt 38, and the supporting bolt 31, the pressing bolt 38 and the V-shaped pressing plates 37 are connected in a floating mode through fixing plates 33, second nuts 36 and bolts 34. Specifically, as shown in fig. 5, the fixing plate 33 has a through hole, the supporting bolt 31 or the pressing bolt 38 passes through the through hole of the fixing plate 33, the supporting bolt 31 and the pressing bolt 38 are respectively provided with a second nut 36 fixed by a set screw 35, and the bolt 34 connects the V-shaped pressing plate 37 and the fixing plate 33 into a whole and is respectively located on both sides of the second nut 36 in a floating state. During clamping, the supporting bolt 31 or the pressing bolt 38 is rotated forwards to press the V-shaped pressing plate 37 to the part until the part is clamped; when the clamping bolt 31 or the pressing bolt 38 is rotated backwards to pull the V-shaped pressing plate 37 away from the part through the second nut 36 and the fixed plate 33.

When the clamping device is in a non-clamping state, the lower plane of the V-shaped pressing plate 37 is in contact with the upper planes on the two sides of the inclined iron guide rail 39, and the effect of preventing the V-shaped pressing plate 37 from rotating along with the clamping device can be achieved at the initial clamping stage.

The end face of the V-shaped pressing plate 37 is provided with a V-shaped groove, so that the V-shaped groove can be conveniently contacted with the outer cylindrical surface of a long hole shaft type multi-boss part. The number of the support bolts 31, the number of the compression bolts 38 and the number of the screw holes on the fixture body 32 are determined according to the length of the long-hole shaft type multi-boss part. The side of the clamp body 32 where the support bolt 31 is assembled serves as a radial horizontal support device 5, and the side of the clamp body 32 where the compression bolt 38 is assembled serves as a radial horizontal clamping device 6. When clamping, the supporting bolts 31 are sequentially rotated until the V-shaped pressing plates 37 of the radial horizontal supporting device 5 are contacted with the multiple boss parts of the long hole shafts, and then the pressing bolts 38 are sequentially rotated, so that the V-shaped pressing plates 37 of the radial horizontal clamping device 6 clamp the multiple boss parts of the long hole shafts.

The radial vertical auxiliary supporting device comprises an inclined iron 41, an inclined iron guide rail 39 and an adjusting screw 42. The wedge rail 39 is fixed to the clamp base plate 8 by a fifth screw 40; the axis of the wedge guide rail 39 is vertical to the axis of the long hole shaft multi-boss part, the wedge 41 is arranged in the wedge guide rail 39, the adjusting screw 42 horizontally penetrates through the clamp body 32, and the tail part of the adjusting screw is contacted with the big end of the wedge 41; when the long hole shaft multi-boss part is clamped by the radial horizontal support and clamping device, the adjusting screw 42 is rotated to adjust the extending length of the adjusting screw 42, the inclined iron 41 is pushed to move forwards along the guide rail inclined plane of the inclined iron guide rail 39, and therefore the height of the inclined iron 41 is adjusted until the inclined iron is contacted with the lower part of the long hole shaft multi-boss part, and the vertical auxiliary support effect is achieved.

The number of the radial horizontal supporting and clamping devices and the number of the radial vertical auxiliary supporting devices 7 can be increased or decreased according to the length of the part, and the adaptability is wide; the clamping force and the auxiliary supporting force adopt a thread structure, and are applied through a torque wrench according to the cutting force, so that the clamping is convenient, and the clamping is reliable.

When the part with the machined axial hole is placed on the clamp designed by the method according to requirements, the part is axially positioned by the axial positioning device, and then is radially positioned, supported and clamped by the radial supporting and clamping device, so that the boss can be machined.

The working principle of the invention is as follows:

when the rapid positioning and clamping device for the long-hole shaft multi-boss parts is used for machining the multiple bosses of the long-hole shaft multi-boss parts, firstly, an axial long hole is machined to the size on proper equipment, then, the long-hole shaft multi-boss parts are sleeved between the axial positioning devices downwards in the radial positioning reference, the handle 22 is rotated, the long-hole shaft multi-boss parts are pressed to the left end, and the long-hole shaft multi-boss parts are stopped until the handle 22 is not rotated. At the moment, the left-right movement, the horizontal translation and the rotation in the horizontal direction and the vertical translation and the rotation of the long-hole shaft multi-boss part are limited to 5 degrees of freedom, so that the boss to be machined is in the correct machining position in the axial direction.

The hook-shaped block 28 of the radial positioning device is rotated, so that the hook-shaped block 28 is vertically placed from the horizontal placement, at the moment, the pressing nail 25 presses the radial positioning reference of the long-hole shaft multi-boss part to the supporting nail 24 under the action of the spring force of the spring 26, at the moment, 1 degree of freedom of the rotation of the long-hole shaft multi-boss part around the axis of the long-hole shaft multi-boss part is limited, and the boss to be machined is located at the correct machining position in the vertical direction.

Sequentially rotating the supporting bolts 31 of the radial horizontal supporting and clamping device to enable the V-shaped pressing plate 37 to be in contact with the long-hole shaft multi-boss part; the hold-down bolt 38 is then rotated in turn until the proper clamping force is achieved, which can be achieved using a torque wrench to achieve the proper clamping force.

The adjusting screw 42 of the radial vertical auxiliary supporting device 7 is rotated to lead the adjusting screw 42 to extend forwards, and the inclined iron 41 is pushed to move forwards along the inclined rail surface of the inclined iron guide rail 39 until the inclined iron is not rotated. At this time, the horizontal plane of the wedge 41 contacts with the lower part of the multiple boss part of the long hole shaft, so as to play a role of vertical auxiliary support, and avoid downward bending deformation of the multiple boss part of the long hole shaft due to overlarge downward cutting force in the machining process.

Therefore, a plurality of bosses on the multi-boss part of the long hole shaft can be processed in sequence. After the processing is finished, the reverse operation is carried out, the multiple boss parts of the long hole shaft can be loosened, and the multiple boss parts of the long hole shaft are taken out from the clamp.

The present invention is not limited to the above-described embodiments, and any obvious improvements, substitutions or modifications can be made by those skilled in the art without departing from the spirit of the present invention.