CN209954449U

CN209954449U - Main shaft assembly of double-surface grinding machine

Info

Publication number: CN209954449U
Application number: CN201920549824.2U
Authority: CN
Inventors: 薛超; 李建伟; 李红波; 薛华
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-04-22
Filing date: 2019-04-22
Publication date: 2020-01-17
Anticipated expiration: 2029-04-22

Abstract

The utility model relates to a digit control machine tool technical field, in particular to double flat grinder's main shaft assembly. The utility model discloses a two flat grinder's main shaft assembly includes: the first end of the main shaft is connected with the grinding wheel, and the second end of the main shaft is provided with a rotary joint; the main shaft sleeve is sleeved on the main shaft; the first bearing group is arranged at the first end of the main shaft and is arranged between the main shaft sleeve and the main shaft; the first bearing group comprises a first radial bearing, a first thrust bearing and a second thrust bearing; a first inner spacer bush is arranged between the first radial bearing and the first thrust bearing, and a first outer spacer bush is arranged between the first thrust bearing and the spindle sleeve; an elastic element is arranged between the second thrust bearing and the first thrust bearing along the axial direction of the main shaft. The utility model discloses a two flat grinder's main shaft assembly is through applying radial pretension and level pressure pretension to the bearing to improve the rigidity and the rotation precision of main shaft at the operation in-process.

Description

Main shaft assembly of double-surface grinding machine

Technical Field

The embodiment of the utility model provides a relate to digit control machine tool technical field, in particular to double flat grinder's main shaft assembly.

Background

The vertical double-surface grinding machine is used for grinding the upper end surface and the lower end surface of a part and is suitable for processing large-batch parts. When the machining accuracy of parts is required to be high, the spindle of the vertical double-plane grinding machine is required to have sufficient rigidity to withstand radial and axial cutting loads and to have high rotational accuracy, and the spindle is required to be capable of continuously and stably operating for a long time. Therefore, the bearing structure of the main shaft needs to be designed reasonably to improve the rigidity and the rotational accuracy of the main shaft during operation and enable the main shaft to bear larger load.

The bearing structure of the main shaft of the vertical double-plane grinding machine in the prior art mainly adopts a structure that a bidirectional angular contact ball bearing and a double-row cylindrical roller bearing are combined and paired for use or a plurality of groups of unidirectional angular contact ball bearings and double-row cylindrical roller bearings are combined and paired for use. However, the spindle using these bearing structures has limited axial rigidity and can only perform small-cut grinding, and heavy-cut large-cut grinding is not possible because of large axial force during heavy-cut grinding. In addition, during operation of the vertical twin surface grinder, a temperature difference may be formed between the spindle and the bearing housing, since the temperature of the spindle generally varies faster than the temperature of the bearing housing. After the main shaft works for a long time, because the bearing inner ring generates heat, the spacer bushes of the main shaft and the bearing inner ring expand faster than the spacer bushes of the bearing seat and the bearing outer ring, so that the main shaft extends, the bearing bears preload and the rigidity of the main shaft is reduced, and the rotation precision is poor.

SUMMERY OF THE UTILITY MODEL

The embodiment of the utility model provides a two flat grinder's main shaft assembly is through applying radial pretension and level pressure pretension to the bearing to improve the rigidity and the rotation precision of main shaft in the operation process.

In order to solve the technical problem, the utility model provides a following technical scheme:

the utility model provides a two flat grinder's main shaft subassembly, include:

the first end of the main shaft is connected with the grinding wheel, and the second end of the main shaft is provided with a rotary joint;

the main shaft sleeve is sleeved on the main shaft;

the first bearing group is arranged at the first end of the main shaft and is arranged between the main shaft sleeve and the main shaft; the first bearing group comprises a first radial bearing, a first thrust bearing and a second thrust bearing, and the first radial bearing, the first thrust bearing and the second thrust bearing are sequentially sleeved on the main shaft from the first end of the main shaft to the second end of the main shaft;

a first inner spacer bush is arranged between the first radial bearing and the first thrust bearing, and a first outer spacer bush is arranged between the first thrust bearing and the spindle sleeve; a thrust bearing seat is arranged between the second thrust bearing and the first thrust bearing, a first groove used for accommodating the first thrust bearing and a second groove used for accommodating the second thrust bearing are respectively arranged at two ends of the thrust bearing seat, a mounting hole is formed in the bottom of the second groove along the axial direction of the thrust bearing seat, and an elastic element is arranged in the mounting hole along the axial direction of the main shaft.

Furthermore, a flange is arranged at the first end of the main shaft and is connected with the grinding wheel through a flange plate.

Furthermore, a front gland is arranged between the main shaft sleeve and the flange, a first concave-convex surface is arranged on the surface of the flange opposite to the front gland, and an adjusting gasket and a rubber ring are arranged between the front gland and the main shaft sleeve.

Furthermore, a second concave-convex surface corresponding to the first concave-convex surface is arranged on the surface of the front gland, which is opposite to the flange.

Furthermore, the front gland extends towards the main shaft to form an extension part, the extension part is in contact with the first centering bearing, a front spacer bush is arranged in a space among the extension part, the first centering bearing and the flange, and a sealing ring is arranged in a space among the extension part, the front spacer bush and the flange.

Furthermore, the main shaft is further sleeved with a first locking nut, the first locking nut is arranged on one side, close to the second end of the main shaft, of the second thrust bearing, and a first nut spacer bush is arranged between the first locking nut and the second thrust bearing.

Furthermore, a second axial bearing is sleeved on the second end, close to the main shaft, of the main shaft, and the second axial bearing is arranged between the main shaft and the main shaft sleeve.

Furthermore, a second inner spacer bush, a second outer spacer bush, a rear gland, a second nut spacer bush and a second locking nut are further sleeved on the main shaft, the second inner spacer bush and the second outer spacer bush are arranged on one side, close to the first end of the main shaft, of the second axial bearing, and the rear gland, the second nut spacer bush and the second locking nut are sequentially arranged on one side, close to the second end of the main shaft, of the second axial bearing.

Based on the above disclosure, the utility model discloses beneficial effect lies in:

the utility model discloses two flat grinder's main shaft assembly, the first bearing group that sets up on its main shaft includes first radial bearing, first thrust bearing and second thrust bearing, can be through first interior spacer, radial pretension is implemented to first bearing to first spacer and first lock nut, and the elastic element through the axial setting implements axial pretension to first thrust bearing and second thrust bearing, in order each bearing can keep setting for the preload when the extension of main shaft thermal expansion, thereby guarantee the rigidity and the rotation precision of main shaft.

Drawings

Fig. 1 is a schematic structural view of a spindle assembly of a double-surface grinding machine according to an embodiment of the present invention;

FIG. 2 is an enlarged view of a portion A of FIG. 1;

fig. 3 is a schematic structural diagram of a thrust bearing seat in an embodiment of the present invention;

fig. 4 is a cross-sectional view of a thrust bearing block in an embodiment of the present invention;

fig. 5 is a cross-sectional view of a thrust bearing block in another embodiment of the present invention;

fig. 6 is an axial view of a spindle assembly of a double surface grinding machine according to an embodiment of the present invention.

Reference numerals: 1. a main shaft; 2. a front gland; 3. adjusting the gasket; 4. a front spacer sleeve; 5. a first radial bearing; 6. a first inner spacer sleeve; 7. a first outer spacer sleeve; 8. a first thrust bearing; 9. a thrust bearing seat; 10. a second thrust bearing; 11. a first nut spacer; 12. a first lock nut; 13. a second inner spacer sleeve; 14. a second outer spacer sleeve; 15. a second radial bearing; 16. a rear gland; 17. a second nut spacer; 18. a second lock nut; 19. a screw rod connecting seat; 20. a main shaft sleeve; 21. an elastic element; 22. a rubber ring; 23. a seal ring; 24. a flange plate; 25. a grinding wheel; 26. a rotary joint; 27. a balance connecting seat; 91. and (7) installing holes.

Detailed Description

The following detailed description of the embodiments of the present invention is provided with reference to the accompanying drawings, but not intended to limit the invention thereto.

It will be understood that various modifications may be made to the embodiments disclosed herein. Accordingly, the foregoing description should not be construed as limiting, but merely as exemplifications of embodiments. Other modifications will occur to those skilled in the art within the scope and spirit of the disclosure.

Those skilled in the art will appreciate that to meet the requirements of stiffness and rotational accuracy of the spindle, it is desirable to properly configure the spindle with bearings to apply the proper preload to the bearings when the spindle is assembled. The bearing is pre-tightened by adjusting the play of the bearing, and an axial force is applied to the inner ring or the outer ring of the bearing when the bearing is assembled so as to eliminate the bearing play and generate pre-deformation when the rolling bodies are contacted with the inner ring and the outer ring. In the operation process of the main shaft, the preload of the bearing can be changed continuously due to the influence of factors such as the main shaft elongation caused by the heating of the bearing and the like: if the preload is increased, the expansion of the inner ring and the contraction of the outer ring of the bearing can be caused, the friction force between the rolling body and the raceway of the bearing is increased, the abrasion is aggravated, the service life of the bearing is shortened, and the bearing is blocked or burnt seriously; if the preload becomes small, the influence of the reduction of the rigidity of the main shaft and the reduction of the rotational accuracy occurs.

Therefore, according to the working mode and the stress state of the grinding machine, a proper bearing configuration is selected and used to form a main shaft assembly together with the main shaft, so that the rigidity and the rotation precision of the main shaft in the working state are improved, and a larger load can be borne.

The embodiment of the utility model provides a two flat grinder's that can realize above-mentioned effect main shaft assembly. The spindle assembly of the double surface grinding machine according to the embodiment of the present invention will be described in detail with reference to the accompanying drawings.

As shown in fig. 1-2, the spindle assembly of the double-surface grinding machine according to the embodiment of the present invention includes a spindle 1, a spindle sleeve 20, and a first bearing set. The first end of the main shaft 1 is connected with a grinding wheel 25, and the second end of the main shaft 1 is provided with a rotary joint 26. The main shaft sleeve 20 is coaxially sleeved on the main shaft 1 with the main shaft 1. The first bearing set is disposed at a first end of the spindle 1 and between the spindle sleeve 20 and the spindle 1. Specifically, the first bearing group includes a first radial bearing 5, a first thrust bearing 8 and a second thrust bearing 10, and the first radial bearing 5, the first thrust bearing 8 and the second thrust bearing 10 are sequentially sleeved on the main shaft 1 from the first end of the main shaft 1 to the second end of the main shaft 1. A first inner spacer 6 is arranged between the first radial bearing 5 and the first thrust bearing 8, and a first outer spacer 7 is arranged between the first thrust bearing 8 and the spindle sleeve 20; an elastic element 21 is arranged between the second thrust bearing 10 and the first thrust bearing 8 along the axial direction of the main shaft 1.

Because the utility model discloses the first bearing group that sets up on main shaft 1 of embodiment includes first radial bearing 5, first thrust bearing 8 and second thrust bearing 10, consequently, the embodiment of the utility model provides a can implement radial pretension to first radial bearing 5 through first inner spacer 6 and first outer spacer 7 to elastic element 21 through the axial setting implements axial pretension to first thrust bearing 8 and second thrust bearing 10, can keep setting for the preload with each bearing when main shaft 1 thermal expansion extension, thereby guarantees the rigidity and the rotational accuracy of main shaft 1.

In the embodiment of the present invention, the first radial bearing 5 may be a taper hole double row cylindrical roller bearing, and the first thrust bearing 8 and the second thrust bearing 10 may be an one-way thrust ball bearing or an one-way thrust cylindrical roller bearing. Therefore, the embodiment of the utility model provides a pair the use through adopting taper hole double row cylindrical roller bearing and thrust bearing and can make main shaft axial rigidity reinforcing, be applicable to the heavy load grinding.

As shown in fig. 1, the main spindle 1 has a center hole, and the center hole is permeable to water and plays a cooling role during grinding. The first end of the main shaft 1 is provided with a flange which is connected with a grinding wheel 25 through a flange plate 24. Specifically, the flange 24 is fixed to the grinding wheel 25, and the flange of the spindle 1 is fixedly connected to the flange 24 by bolts.

In the embodiment of the present invention, in order to ensure the relative position between the spindle sleeve 20 and the spindle 1 and the flange 24, a front gland 2 is provided between the spindle sleeve 20 and the flange of the spindle 1. Specifically, the adjusting shim 3 and the rubber ring 22 may be provided between the front gland 2 and the spindle cover 20, thereby ensuring sealability between the front gland 2 and the spindle cover 20.

In order to ensure that the front gland 2 and the flange have good sealing performance, the surface of the flange opposite to the front gland 2 is provided with a first concave-convex surface, and the surface of the front gland 2 opposite to the flange is provided with a second concave-convex surface corresponding to the first concave-convex surface, so that non-contact gap sealing is formed through the matching of the first concave-convex surface and the second concave-convex surface.

For further improvement, the front gland 2 has an extension part extending toward the main shaft 1 (i.e., the front gland 2 is toward its axial direction), and the extension part contacts with the first centering bearing 5. Because the end surface of the first radial bearing 5 near one end of the grinding wheel 25 is positioned inside the spindle sleeve 20, the extension part and the front gland 2 form a stepped surface, and the thickness of the extension part is smaller than that of other parts of the front gland 2. Since the extension is not in contact with the main shaft 1, a space is formed between the extension, the first radial bearing 5 and the flange, and a front spacer 4 is required to be provided in the space between the extension, the first radial bearing 5 and the flange in order to enhance the sealing property. Because the extension part and the front gland 2 form a stepped surface, a space is formed among the extension part, the front spacer 4 and the flange, and a sealing ring 23 is required to be arranged in the space among the extension part, the front spacer 4 and the flange so as to improve the sealing performance of the extension part, the front spacer 4 and the flange.

In the embodiment of the present invention, the sealing ring 23 may form a contact seal. The seal ring 23 may be a V-shaped seal ring, a Y-shaped seal ring, or a lip-shaped seal ring.

Therefore, the embodiment of the utility model provides a can combine non-contact and two kinds of sealing methods of contact to prevent that grinding fluid from getting into the main shaft, pollute the bearing, cause the early damage of bearing.

As shown in fig. 1 and 2, in the embodiment of the present invention, a thrust bearing seat 9 is disposed between the second thrust bearing 10 and the first thrust bearing 8, and the elastic element 21 is disposed in the thrust bearing seat 9 along the axial direction of the thrust bearing seat 9.

As shown in fig. 3, two ends of the thrust bearing seat 9 are respectively provided with a first groove for accommodating the first thrust bearing 8 and a second groove for accommodating the second thrust bearing 10, a groove bottom of the second groove is provided with a mounting hole 91, and the elastic element is arranged in the mounting hole 91. The bottom surface of the second groove of the thrust bearing seat 9 for accommodating the second thrust bearing 10 is circumferentially distributed with a plurality of mounting holes 91, each mounting hole 91 is arranged along the axial direction of the thrust bearing seat, and the number of the mounting holes 91 is the same as that of the elastic elements 21. The elastic element 21 is disposed in the mounting hole 91, wherein the elastic element 21 may be a coil spring or a belleville spring.

As shown in fig. 4, in an embodiment of the present invention, the mounting hole 91 is a blind hole, one end of each elastic element 21 abuts against the second thrust bearing 10, and the other end is disposed on the bottom surface of the mounting hole 91. In another embodiment of the present invention, as shown in fig. 5, the mounting hole 91 is a through hole, and one end of each elastic element 21 is abutted against the second thrust bearing 10 and the other end is abutted against the first thrust bearing 8.

In the embodiment of the present invention, the main shaft 1 is further sleeved with a first lock nut 12, the first lock nut 12 is disposed on one side of the second thrust bearing 10 close to the second end of the main shaft 1, a first nut spacer 11 is disposed between the first lock nut 12 and the second thrust bearing 10, and the first lock nut 12 plays a locking role for the first bearing set.

The pretension principle of the first bearing group provided by the embodiment of the utility model is that the inner ring of the first axial bearing 5 is in interference fit with the main shaft 1 by configuring the thickness dimension of the front spacer 4, so that the main shaft 1 forms radial centering and pretension, and the radial rigidity and the rotation precision of the main shaft 1 are ensured; meanwhile, as the elastic elements 21 in the mounting holes 91 are slightly deeper than the holes of the mounting holes 91 under the free and unstressed condition, when the first locking nut 12 is locked, the elastic elements 21 are slightly compressed, so that the second thrust bearing 10 is attached to the bottom surface of the second groove of the thrust bearing seat 9, the axial pre-tightening of the first thrust bearing 8 and the second thrust bearing 10 is realized, and the main shaft 1 obtains good axial rigidity. When the main shaft 1 runs at a low speed, the thrust bearing seat 9 plays a role of a rigid spacer bush; when the main shaft 1 runs for a long time or runs at a high speed, the bearing temperature of the main shaft 1 rises to heat the main shaft 1, so that the main shaft 1 generates elongation deformation along the axial direction of the main shaft 1, at the moment, the elongation can be compensated through the elongation of the elastic element 21, the elastic element 21 arranged in the thrust bearing seat 9 plays a role of constant pressure pre-tightening, so that the main shaft 1 can realize axial floating during the temperature change, the initial axial pre-load of the main shaft 1 cannot be obviously increased or reduced, namely, the axial rigidity of the main shaft 1 is ensured, and the performance of the main shaft 1 is more stable.

In the embodiment of the present invention, as shown in fig. 1, the second end sleeve close to the main shaft 1 on the main shaft 1 is provided with the second axial bearing 15, and the second axial bearing 15 is disposed between the main shaft 1 and the main shaft sleeve 20. The spindle 1 is further sleeved with a second inner spacer 13, a second outer spacer 14, a rear gland 16, a second nut spacer 17 and a second lock nut 18, the second inner spacer 13 and the second outer spacer 14 are arranged on one side, close to the first end of the spindle 1, of the second axial bearing 15, and the rear gland 16, the second nut spacer 17 and the second lock nut 18 are sequentially arranged on one side, close to the second end of the spindle 1, of the second axial bearing 15.

Specifically, the positions of the main shaft 1 and the main shaft sleeve 20 for accommodating the second axial bearing 15 are respectively provided with a step surface, a second inner spacer 13 is further arranged between the step surface of the main shaft 1 and the second axial bearing 15, a second outer spacer 14 is further arranged between the step surface of the main shaft sleeve 20 and the second axial bearing 15, and the main shaft 1 is further sleeved with a rear gland 16 for limiting the axial position of the second axial bearing 15, a second nut spacer 17 and a second lock nut 18.

Wherein the second lock nut 18 is axially locked so that the lower end face of the outer ring of the second axial bearing 15 is axially fastened to the rear gland 16 through the second outer spacer 14. Although the inner ring and the outer ring of the second axial bearing 15 at the second end of the main shaft 1 are fixed, because the second axial bearing 15 adopts a taper hole double-row cylindrical roller bearing, the inner ring of the second axial bearing 15 is in interference fit with the step surface of the main shaft by setting the thickness dimension of the second inner spacer 14, so that the main shaft 1 forms radial centering and pre-tightening, when the main shaft 1 runs at high speed, the bearing temperature of the main shaft 1 rises to heat the main shaft, and the main shaft 1 generates elongation deformation along the axial direction, the displacement and expansion of the first end of the main shaft 1 can be carried out in the radial bearing 15, and adverse effects of overlarge pre-loading, serious bearing heating and the like cannot be caused.

As shown in fig. 6, in the embodiment of the present invention, a screw rod connecting seat 19 and two balance connecting seats 27 are further disposed outside the middle section of the spindle sleeve 20. The screw rod connecting seat 19 is used for connecting a feeding component (not shown), and the balance connecting seat 27 is used for connecting a balancing component (not shown) in feeding.

The embodiment of the utility model provides an installation method of two flat grinder's main shaft subassembly as follows:

firstly, preparing the needed purchased parts, processing the processed parts in place according to a drawing, wherein the front spacer 4, the second inner spacer 13 and the adjusting shim 3 are subjected to matched grinding when allowance is left for installation.

Secondly, the first radial bearing 5 needs to adjust the clearance during installation, and the method for adjusting the clearance is to enable the radial clearance of the first radial bearing 5 to reach a specified value by adjusting the thickness dimension of the front spacer 4, so that a certain preload is obtained. The specific steps of adjusting the play are as follows: (1) the inner ring of the first centering bearing 5 is lightly arranged at the position, close to the flange, of the first end of the main shaft 1; (2) measuring the distance between the end surface of the inner ring of the first radial bearing 5 and the end surface of the shaft shoulder of the main shaft 1 by using a block gauge; (3) the temporarily processed front spacer 4 is installed on the main shaft 1 until the width of the temporarily processed front spacer 4 reaches a measured value (4), and then the inner ring of the first radial bearing 5 is installed on the main shaft 1; (5) the dial indicator is abutted against the outer ring of the first centripetal bearing 5, the outer ring is moved along the radial direction of the first centripetal bearing 5, and the radial play of the first centripetal bearing 5 at the moment is measured; (6) detaching a first radial bearing 5 and a front spacer 4 from a shaft 1; (7) according to a preset radial play value and the taper, calculating the inner ring extrusion amount of the target residual radial play, and obtaining the width size of the required front spacer 4; (8) the thickness dimension of the front spacer 4 is ground to the required width dimension; (9) installing a first centripetal bearing 5 and a front spacer 4 on a main shaft 1, and fully pressing an inner ring of the first centripetal bearing 5 to ensure that the end surface of the front spacer 4 is completely attached to each matching surface of the end surface of the inner ring of the first centripetal bearing 5 and the end surface of the front spacer 4 and the end surface of a shaft shoulder of the main shaft 1; (10) a second inner spacer 13 was milled in the same way.

Thirdly, the front spacer 4 is firstly installed on a shaft shoulder at the first end of the main shaft 1, the front end cover 2, the rubber ring 22 and the sealing ring 23 are placed at the first end of the main shaft 1 to be installed, the first axial bearing 5 is installed in the main shaft 1, then the first inner spacer 6, the first outer spacer 7, the first thrust bearing 8, the thrust bearing seat 9, the elastic element 21, the second axial bearing 10, the first nut spacer 11 and the first lock nut 12 are sequentially sleeved on the main shaft 1, and the first lock nut 12 is screwed by a torque wrench according to a preset torque.

Fourthly, the assembled components are installed into a spindle sleeve 20, the distance between the end face, close to the grinding wheel 25, of the spindle sleeve 20 and the front end cover 2 is measured, the thickness of the adjusting gasket 3 is matched and ground according to the value, the adjusting gasket 3 is installed between the spindle sleeve 20 and the front end cover 2 after matching and grinding, then the screws of the front end cover 2 and the spindle sleeve 20 are locked, and the installation of one end, close to the grinding wheel 25, of the spindle assembly is completed.

Fifthly, mounting a component of the spindle component far away from one end of the grinding wheel 25: and (3) installing the second inner spacer 13, the second outer spacer 14, the second radial bearing 15 and the second nut spacer 17 which are well matched and ground into the spindle 1 and the spindle sleeve 20, locking the second locking nut 18 according to a specified torque to fix the inner ring of the second radial bearing 15, and fastening the outer ring of the second radial bearing 15 by the gland 16 after installation.

In the embodiment of the present invention, the vertical double flat surface grinding machine in which the rotation axis of the grinding wheel is in the vertical direction has been described, but the present invention is not limited thereto, and for example, the present invention can also be applied to a horizontal double flat surface grinding machine in which the rotation axis of the grinding wheel is in the horizontal direction.

The above embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and the protection scope of the present invention is defined by the claims. Various modifications and equivalents of the invention can be made by those skilled in the art within the spirit and scope of the invention, and such modifications and equivalents should also be considered as falling within the scope of the invention.

Claims

1. A spindle assembly for a twin surface grinding machine, comprising:

the grinding machine comprises a main shaft (1), wherein a first end of the main shaft (1) is connected with a grinding wheel (25), and a second end of the main shaft is provided with a rotary joint (26);

the main shaft sleeve (20), the main shaft sleeve (20) is sleeved on the main shaft (1);

a first bearing set disposed at a first end of the spindle (1) and disposed between the spindle cover (20) and the spindle (1); the first bearing group comprises a first radial bearing (5), a first thrust bearing (8) and a second thrust bearing (10), and the first radial bearing (5), the first thrust bearing (8) and the second thrust bearing (10) are sequentially sleeved on the main shaft (1) from the first end of the main shaft (1) to the second end of the main shaft (1);

a first inner spacer sleeve (6) is arranged between the first radial bearing (5) and the first thrust bearing (8), and a first outer spacer sleeve (7) is arranged between the first thrust bearing (8) and the spindle sleeve (20); second thrust bearing (10) with be equipped with thrust bearing frame (9) between first thrust bearing (8), the both ends of thrust bearing frame (9) are equipped with respectively and are used for holding the first recess of first thrust bearing (8) and are used for holding the second recess of second thrust bearing (10), the tank bottom of second recess is followed the axial of thrust bearing frame (9) is equipped with mounting hole (91), follow in mounting hole (91) the axial of main shaft is equipped with elastic element (21).

2. Spindle assembly for a twin surface grinding machine as claimed in claim 1 characterised in that the first end of the spindle (1) is provided with a flange which is connected to the grinding wheel (25) by means of a flange (24).

3. The spindle assembly of a twin surface grinder as set forth in claim 2, characterized in that a front gland (2) is provided between the spindle housing (20) and the flange of the spindle (1), and a spacer (3) and a rubber ring (22) are provided between the front gland (2) and the spindle housing (20).

4. The spindle assembly of a twin surface grinder as set forth in claim 3, wherein the surface of the flange opposite to the front gland (2) is provided with a first concavo-convex surface, and the surface of the front gland (2) opposite to the flange is provided with a second concavo-convex surface corresponding to the first concavo-convex surface.

5. The spindle assembly of a twin surface grinder as set forth in claim 4, characterized in that the front gland (2) has an extension extending toward the spindle (1), the extension contacting the first radial bearing (5), a front spacer (4) being provided in a space between the extension, the first radial bearing (5) and the flange, and a seal ring (23) being provided in a space between the extension, the front spacer (4) and the flange.

6. The main shaft assembly of the twin surface grinding machine according to claim 1, characterized in that the main shaft (1) is further sleeved with a first lock nut (12), the first lock nut (12) is arranged on the side of the second thrust bearing (10) close to the second end of the main shaft (1), and a first nut spacer (11) is arranged between the first lock nut (12) and the second thrust bearing (10).

7. The spindle assembly of a twin surface grinding machine according to claim 1, characterized in that a second radial bearing (15) is fitted on the spindle (1) near a second end of the spindle (1), and the second radial bearing (15) is disposed between the spindle (1) and the spindle sleeve (20).

8. The main shaft assembly of the double-surface grinder as claimed in claim 7, wherein the main shaft (1) is further sleeved with a second inner spacer (13), a second outer spacer (14), a rear gland (16), a second nut spacer (17) and a second lock nut (18), the second inner spacer (13) and the second outer spacer (14) are arranged on one side of the second radial bearing (15) close to the first end of the main shaft (1), and the rear gland (16), the second nut spacer (17) and the second lock nut (18) are sequentially arranged on one side of the second radial bearing (15) close to the second end of the main shaft (1).