CN209878818U

CN209878818U - Test jig

Info

Publication number: CN209878818U
Application number: CN201920386432.9U
Authority: CN
Inventors: 孙全军; 孙理军
Original assignee: Shanghai Di Jia Plant Equipment Co Ltd
Current assignee: Shanghai Di Jia Plant Equipment Co Ltd
Priority date: 2019-03-25
Filing date: 2019-03-25
Publication date: 2019-12-31
Anticipated expiration: 2029-03-25

Abstract

The utility model relates to the technical field of auxiliary devices of test equipment, in particular to a test frame which can limit and fix circuit boards with various specifications; the test device comprises a bottom plate, a workbench, a left support plate, a right support plate, a left clamping plate, a right clamping plate, a support plate, a fixed plate, a telescopic column, a spring, a pressing plate, a test plate, a first left stabilizing plate, a second left stabilizing plate and a left slide bar, wherein a telescopic hole is longitudinally formed in the central area of the top end of the fixed plate, a plurality of groups of test probes are arranged at the bottom end of the test plate, and a left through hole is longitudinally formed in the left rear side of the top; still include left slider, right slider, dwang, motor and mount pad, workstation bottom left half regional and right half regional left sliding tray and right sliding tray of being provided with respectively, workstation top left half regional and right half regional left hole and right-hand hole of being provided with respectively, left extension board and right extension board left side wall central area transversely are provided with the hole of turning left and the hole of turning right respectively.

Description

Test jig

Technical Field

The utility model relates to a test equipment auxiliary device's technical field especially relates to a test jig.

Background

As is well known, a test rack is an auxiliary device for detecting the electrification of a circuit board, and is widely used in the field of test equipment; the existing test frame comprises a bottom plate, a workbench, a left support plate, a right support plate, a left clamping plate, a right clamping plate, a support plate, a fixed plate, a telescopic column, a spring, a press plate, a test plate, a first left stabilizing plate, a second left stabilizing plate and a left slide bar, wherein the top ends of the left support plate and the right support plate are respectively connected with the left half area and the right half area at the bottom end of the workbench, the bottom ends of the left support plate and the right support plate are respectively connected with the left half area and the right half area at the top end of the bottom plate, the bottom ends of the left clamping plate and the right clamping plate are respectively connected with the left half area and the right half area at the top end of the workbench, the bottom end of the support plate is connected with the rear side of the central area at the top end of the bottom plate, the rear end of the fixed plate is connected with the upper half area of the front side wall of the support, the bottom end of the telescopic column sequentially penetrates through the spring and the telescopic hole and is connected with the central area of the top end of the test board, a plurality of groups of test probes are arranged at the bottom end of the test board, a left through hole is longitudinally formed in the left rear side of the top end of the test board, the rear ends of the first left stabilizing plate and the second left stabilizing plate are connected with the left half area of the front side wall of the support plate, the top end of the left slide rod is connected with the central area of the bottom end of the first left stabilizing plate, and the bottom end of the left slide rod penetrates through the left; when the existing test rack is used, a worker firstly places a circuit board on a workbench, the left clamping board and the right clamping board are limited and fixed, a plurality of groups of test probes are electrically connected with an external control device and a display device, the board is manually pressed downwards, a press plate drives a test board to move downwards, the circuit board is subjected to power-on test through the plurality of groups of test probes, and information detected by the plurality of groups of test probes is displayed through the external display device; the existing test frame is found in use, the circuit board with one specification size can be limited and fixed, and the use limitation is high.

SUMMERY OF THE UTILITY MODEL

In order to solve the technical problem, the utility model provides a can carry out spacing fixed to the circuit board of multiple specification size, reduce the test jig that uses the limitation.

The utility model relates to a test jig, which comprises a bottom plate, a workbench, a left support plate, a right support plate, a left clamping plate, a right clamping plate, a support plate, a fixed plate, a telescopic column, a spring, a press plate, a test plate, a first left stabilizing plate, a second left stabilizing plate and a left slide bar, wherein the top ends of the left support plate and the right support plate are respectively connected with the left half area and the right half area at the bottom end of the workbench, the bottom ends of the left support plate and the right support plate are respectively connected with the left half area and the right half area at the top end of the bottom plate, the bottom ends of the left clamping plate and the right clamping plate are respectively connected with the left half area and the right half area at the top end of the workbench, the bottom end of the support plate is connected with the rear side of the central area at the top end of the bottom plate, the rear end of the fixed plate is connected with the upper half area of the front side wall of the, the bottom end of the telescopic column sequentially penetrates through the spring and the telescopic hole and is connected with the central area of the top end of the test board, a plurality of groups of test probes are arranged at the bottom end of the test board, a left through hole is longitudinally formed in the left rear side of the top end of the test board, the rear ends of the first left stabilizing plate and the second left stabilizing plate are connected with the left half area of the front side wall of the support plate, the top end of the left slide rod is connected with the central area of the bottom end of the first left stabilizing plate, and the bottom end of the left slide rod penetrates through the left; the left sliding block and the right sliding groove are respectively arranged at the left half area and the right half area of the bottom end of the workbench, the left half area and the right half area of the top end of the workbench are respectively provided with a left hole and a right hole, the left hole and the right hole are respectively communicated with the left sliding groove and the right sliding groove, the top ends of the left sliding block and the right sliding block are respectively fixed in the left sliding groove and the right sliding groove in a sliding way, the bottom ends of the left clamping plate and the right clamping plate respectively penetrate through the left hole and the right hole and are respectively connected with the top ends of the left sliding block and the right sliding block, the central areas of the left side wall of the left supporting plate and the left side wall of the right supporting plate are respectively and transversely provided with a left rotating hole and a right rotating hole, the left half area and the right half area of the outer side wall of the rotating rod are respectively provided with a left external thread and a right external thread, the left external thread and the right external thread are opposite in rotating, the dwang left end passes the left turn hole and is connected with motor right part output, and the dwang right-hand member inserts to the right turn downthehole, the mount pad bottom is connected with the half regional left side on bottom plate top, and the mount pad top is connected with the motor bottom.

The utility model discloses a test jig still includes left stabilizer bar and right stabilizer bar, and left slider and right slider left side wall first region transversely are provided with left perforating hole and right perforating hole respectively, left stabilizer bar and right stabilizer bar left end respectively with left sliding tray and right sliding tray in left side wall central authorities regional connection, left stabilizer bar and right stabilizer bar right-hand member pass left perforating hole and right perforating hole respectively and respectively with left sliding tray and right sliding tray in right side wall central authorities regional connection.

The utility model discloses a test jig still includes first right steadying plate, second right steadying plate and right slide bar, surveys test panel top right rear side and vertically is provided with right through-hole, first right steadying plate and second right steadying plate rear end all with the backup pad before the half regional connection on the right side of lateral wall, right slide bar top and first right steadying plate bottom central authorities are regional to be connected, right slide bar bottom pass right through-hole and with second right steadying plate top central authorities regional connection.

The utility model discloses a test jig still includes dead lever and pull rod, the dead lever bottom is connected with clamp plate top central authorities region, pull rod left end and the first regional connection of dead lever right side wall.

The utility model discloses a test jig is provided with first left ball bearing and first right ball bearing between dwang and left turn hole and the right turn downthehole wall respectively.

The utility model discloses a test jig still includes the accessory plate, the accessory plate bottom is connected with bottom plate top central authorities region, and the first region of accessory plate left side wall transversely is provided with the intercommunicating pore, the dwang pass the intercommunicating pore and with be provided with second ball bearing between the intercommunicating pore inside wall.

The utility model discloses a test jig, left screens board right side wall and right screens board left side wall first region are provided with left slipmat and right slipmat respectively.

The utility model discloses a test jig still includes four group's landing legs and four group's gyro wheels, four group's landing leg tops are connected with bottom plate bottom left front side, right front side, left rear side and right rear side respectively, four group's gyro wheels are rotatable installation respectively in four group's landing leg bottoms.

Compared with the prior art, the beneficial effects of the utility model are that: firstly, a circuit board is placed in the central area of the top end of a workbench, a motor is turned on, the motor can rotate forwards and backwards, the motor drives a rotating rod to rotate, the left half area and the right half area of the outer side wall of the rotating rod are respectively provided with a left external thread and a right external thread, the rotating directions of the left external thread and the right external thread are opposite, a left sliding block and a right sliding block are respectively sleeved in the left half area and the right half area of the outer side of the rotating rod in a screw manner, the rotating rod can rotate forwards and backwards through the driving of the motor, and further the left sliding block and the right sliding block can move oppositely or oppositely, because the bottom ends of a left clamping plate and a right clamping plate are respectively connected with the top ends of the left sliding block and the right sliding block, the left clamping plate and the right clamping plate can move oppositely or oppositely, when the left clamping plate and the right clamping plate move oppositely, the, and then can realize compressing tightly fixedly to the circuit board of multiple specification size, reduce and use the limitation.

Drawings

Fig. 1 is a schematic structural diagram of the present invention;

FIG. 2 is a schematic left side view of a part of the structure of the present invention;

FIG. 3 is an enlarged view of a portion of FIG. 1;

FIG. 4 is an enlarged view of a portion B of FIG. 1;

in the drawings, the reference numbers: 1. a base plate; 2. a work table; 3. a left support plate; 4. a right support plate; 5. a left clamping plate; 6. a right clamping plate; 7. a support plate; 8. a fixing plate; 9. a telescopic column; 10. a spring; 11. pressing a plate; 12. a test board; 13. a first left stabilising plate; 14. a second left stabilising plate; 15. a left slide bar; 16. testing the probe; 17. a left slider; 18. a right slider; 19. rotating the rod; 20. a motor; 21. a mounting seat; 22. a left stabilizer bar; 23. a right stabilizer bar; 24. a first right stabilising plate; 25. a second right stabilising plate; 26. a right slide bar; 27. fixing the rod; 28. a pull rod; 29. a first left ball bearing; 30. a first right ball bearing; 31. an auxiliary plate; 32. a second ball bearing; 33. a left non-slip mat; 34. a right anti-skid pad; 35. a support leg; 36. and a roller.

Detailed Description

The following detailed description of the embodiments of the present invention is provided with reference to the accompanying drawings and examples. The following examples are intended to illustrate the invention, but are not intended to limit the scope of the invention.

As shown in figures 1 to 4, the utility model relates to a test jig, which comprises a bottom plate 1, a workbench 2, a left support plate 3, a right support plate 4, a left clamping plate 5, a right clamping plate 6, a support plate 7, a fixed plate 8, a telescopic column 9, a spring 10, a press plate 11, a test plate 12, a first left stabilizing plate 13, a second left stabilizing plate 14 and a left slide bar 15, wherein the top ends of the left support plate 3 and the right support plate 4 are respectively connected with the left half area and the right half area at the bottom end of the workbench 2, the bottom ends of the left support plate 3 and the right support plate 4 are respectively connected with the left half area and the right half area at the top end of the bottom plate 1, the bottom ends of the left clamping plate 5 and the right clamping plate 6 are respectively connected with the left half area and the right half area at the top end of the workbench 2, the bottom end of the support plate 7 is connected with the rear side of the central area at the top end of the, the top end of a spring 10 is connected with the central area of the bottom end of a pressing plate 11, the bottom end of the spring 10 is connected with the central area of the top end of a fixing plate 8, the top end of a telescopic column 9 is connected with the central area of the bottom end of the pressing plate 11, the bottom end of the telescopic column 9 sequentially penetrates through the spring 10 and a telescopic hole and is connected with the central area of the top end of a test plate 12, a plurality of groups of test probes 16 are arranged at the bottom end of the test plate 12, a left through hole is longitudinally formed in the left rear side of the top end of the test plate 12, the rear ends of a first left stabilizing plate 13 and a second left stabilizing plate 14 are connected with the left half area of the front side wall of a supporting plate 7, the top end of a left; the left and right clamping plates 5 and 6 respectively penetrate through the left and right holes and are respectively connected with the top ends of the left and right sliders 17 and 18, the central areas of the left side walls of the left support plate 3 and the right support plate 4 are respectively and transversely provided with a left rotating hole and a right rotating hole, the left half area and the right half area of the outer side wall of the rotating rod 19 are respectively provided with a left external thread and a right external thread, the rotating directions of the left external thread and the right external thread are opposite, the left sliding block 17 and the right sliding block 18 are respectively sleeved in the left half area and the right half area outside the rotating rod 19 in a threaded manner, the left end of the rotating rod 19 penetrates through the left rotating hole and is connected with the output end of the right part of the motor 20, the right end of the rotating rod 19 is inserted into the right rotating hole, the bottom end of the installation seat 21 is connected with the left half area at the top end of the bottom plate 1, and the top end of the installation seat 21 is connected with the bottom end of the motor 20; firstly, a circuit board is placed in the central area of the top end of a workbench, a motor is turned on, the motor can rotate forwards and backwards, the motor drives a rotating rod to rotate, the left half area and the right half area of the outer side wall of the rotating rod are respectively provided with a left external thread and a right external thread, the rotating directions of the left external thread and the right external thread are opposite, a left sliding block and a right sliding block are respectively sleeved in the left half area and the right half area of the outer side of the rotating rod in a screw manner, the rotating rod can rotate forwards and backwards through the driving of the motor, and further the left sliding block and the right sliding block can move oppositely or oppositely, because the bottom ends of a left clamping plate and a right clamping plate are respectively connected with the top ends of the left sliding block and the right sliding block, the left clamping plate and the right clamping plate can move oppositely or oppositely, when the left clamping plate and the right clamping plate move oppositely, the, and then can realize compressing tightly fixedly to the circuit board of multiple specification size, reduce and use the limitation.

The utility model discloses a test jig, still include left stabilizer bar 22 and right stabilizer bar 23, left slider 17 and right slider 18 left side wall upper half region transversely is provided with left perforating hole and right perforating hole respectively, left stabilizer bar 22 and right stabilizer bar 23 left end respectively with left side wall central area connection in left sliding tray and the right sliding tray, left stabilizer bar 22 and right stabilizer bar 23 right-hand member pass left perforating hole and right perforating hole respectively and respectively with left sliding tray and right sliding tray right side wall central area connection; the left stabilizer bar and the right stabilizer bar play a limiting role in the left sliding block and the right sliding block respectively, the left sliding block and the right sliding block are prevented from being separated from the left sliding groove and the right sliding groove respectively, and the use reliability is improved.

The utility model discloses a test jig, still include first right stabilizer plate 24, second right stabilizer plate 25 and right slide bar 26, test board 12 top right rear side is vertically provided with right through-hole, first right stabilizer plate 24 and second right stabilizer plate 25 rear end all with backup pad 7 front side wall right half regional connection, right slide bar 26 top is connected with first right stabilizer plate 24 bottom central area, right slide bar 26 bottom passes right through-hole and is connected with second right stabilizer plate 25 top central area; the left sliding rod and the right sliding rod are symmetrically arranged, so that the test board can move up and down more stably, and the use stability is improved.

The utility model discloses a test jig, still include dead lever 27 and pull rod 28, the dead lever 27 bottom is connected with the central area of the top of the pressing plate 11, the left end of the pull rod 28 is connected with the upper half area of the right side wall of the dead lever 27; can be convenient for remove the clamp plate through the pull rod, improve the convenience of use.

In the test frame of the utility model, a first left ball bearing 29 and a first right ball bearing 30 are respectively arranged between the rotating rod 19 and the inner side walls of the left rotating hole and the right rotating hole; first left ball bearing and first right ball bearing can reduce the produced frictional resistance when the dwang rotates, improve and use the ride comfort.

The utility model discloses a test jig, still include accessory plate 31, accessory plate 31 bottom is connected with bottom plate 1 top central area, accessory plate 31 left side wall upper half region transversely is provided with the intercommunicating pore, dwang 19 passes the intercommunicating pore and is provided with second ball bearing 32 with the intercommunicating pore inside wall; the auxiliary plate can play a supporting role for the rotating rod, and the use stability is improved.

In the test jig of the utility model, the upper half areas of the right side wall of the left clamping plate 5 and the left side wall of the right clamping plate 6 are respectively provided with a left non-slip mat 33 and a right non-slip mat 34; the left non-slip mat and the right non-slip mat can enhance the fixing effect on the circuit board and improve the use reliability.

The utility model discloses a test jig, still include four groups of landing legs 35 and four groups of gyro wheels 36, four groups of landing legs 35 top are connected with bottom plate 1 bottom left front side, right front side, left rear side and right rear side respectively, four groups of gyro wheels 36 are rotatable to be installed in four groups of landing legs 35 bottom respectively; four groups of rollers can be convenient for moving the device, and the use flexibility is improved.

The utility model discloses a test jig, when it works, firstly, place the circuit board in the central region of the top of the workbench, turn on the motor, the motor can rotate forward and backward, the motor drives the rotating rod to rotate, the left half region and the right half region of the outer side wall of the rotating rod are respectively provided with a left external thread and a right external thread, and the rotating directions of the left external thread and the right external thread are opposite, the left slider and the right slider are respectively sleeved on the left half region and the right half region outside the rotating rod in a screw-in manner, the rotating rod can rotate forward and backward by the driving of the motor, so that the left slider and the right slider can move relatively or back to back, because the bottom ends of the left clamping plate and the right clamping plate are respectively connected with the top ends of the left slider and the right slider, so that the left clamping plate and the right clamping plate can move relatively or back to back, when the left clamping plate and the right, the circuit board can be released from being compressed and fixed, so that the circuit boards with various specifications can be compressed and fixed, and the use limitation is reduced; the left stabilizer bar and the right stabilizer bar respectively limit the left sliding block and the right sliding block, so that the left sliding block and the right sliding block are prevented from being separated from the left sliding groove and the right sliding groove respectively, and the use reliability is improved; the left sliding rod and the right sliding rod are symmetrically arranged, so that the test board is more stable in the up-and-down movement process, and the use stability is improved; the pressing plate can be conveniently moved through the pull rod, so that the use convenience is improved; the first left ball bearing and the first right ball bearing can reduce the friction resistance generated when the rotating rod rotates, and the use smoothness is improved; the auxiliary plate can support the rotating rod, so that the use stability is improved; the left anti-skid pad and the right anti-skid pad can enhance the fixing effect on the circuit board and improve the use reliability; four groups of rollers can be convenient for moving the device, and the use flexibility is improved.

The utility model discloses a motor that test jig used is purchase from the market, only need install according to the description use can.

The utility model discloses a test jig, above the mounting means, the connected mode or the mode that sets up of all parts are common mechanical system to the concrete structure, model and the coefficient index of all its parts are its from taking the technique, as long as can reach all can implement of its beneficial effect, so do not add at many and give unnecessary details.

In the case of the test rack of the present invention, unless otherwise stated, the terms "up, down, left, right, front, back, inner, and vertical, horizontal" and the like are included in the term, and the terms only represent the orientation of the term in the normal use state, or be a trivial term understood by those skilled in the art, and should not be considered as limiting the term, at the same time, the numerical terms "first," "second," and "third," etc. do not denote any particular quantity or order, but rather are used to distinguish one from another, furthermore, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but also includes other elements not expressly listed or inherent to such process, method, article, or apparatus.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims

1. A test rack comprises a bottom plate (1), a workbench (2), a left support plate (3), a right support plate (4), a left clamping plate (5), a right clamping plate (6), a support plate (7), a fixing plate (8), a telescopic column (9), a spring (10), a pressure plate (11), a test plate (12), a first left stabilizing plate (13), a second left stabilizing plate (14) and a left slide bar (15), wherein the top ends of the left support plate (3) and the right support plate (4) are respectively connected with the left half area and the right half area at the bottom end of the workbench (2), the bottom ends of the left support plate (3) and the right support plate (4) are respectively connected with the left half area and the right half area at the top end of the bottom plate (1), the bottom ends of the left clamping plate (5) and the right clamping plate (6) are respectively connected with the left half area and the right half area at the top end of the workbench (2), the bottom end of the support plate (7), the rear end of a fixed plate (8) is connected with the upper half area of the front side wall of a supporting plate (7), a telescopic hole is longitudinally arranged in the central area of the top end of the fixed plate (8), the top end of a spring (10) is connected with the central area of the bottom end of a pressing plate (11), the bottom end of the spring (10) is connected with the central area of the top end of the fixed plate (8), the top end of a telescopic column (9) is connected with the central area of the bottom end of the pressing plate (11), the bottom end of the telescopic column (9) sequentially penetrates through the spring (10) and the telescopic hole and is connected with the central area of the top end of a testing plate (12), a plurality of groups of testing probes (16) are arranged at the bottom end of the testing plate (12), a left through hole is longitudinally arranged at the left rear side of the top end of the testing plate (12), the rear ends of a first left stabilizing plate (13) and a second left, the bottom end of the left sliding rod (15) penetrates through the left through hole and is connected with the central area of the top end of the second left stabilizing plate (14); the device is characterized by further comprising a left sliding block (17), a right sliding block (18), a rotating rod (19), a motor (20) and a mounting seat (21), wherein a left sliding groove and a right sliding groove are respectively arranged in a left half area and a right half area at the bottom end of the workbench (2), a left hole and a right hole are respectively arranged in a left half area and a right half area at the top end of the workbench (2), the left hole and the right hole are respectively communicated with the left sliding groove and the right sliding groove, the top ends of the left sliding block (17) and the right sliding block (18) are respectively fixed in the left sliding groove and the right sliding groove in a sliding manner, the bottom ends of the left clamping plate (5) and the right clamping plate (6) respectively penetrate through the left hole and the right hole and are respectively connected with the top ends of the left sliding block (17) and the right sliding block (18), a left rotating hole and a right rotating hole are respectively transversely arranged in a central area of a left, dwang (19) lateral wall left side half regional and right half regional left external screw thread and right external screw thread of being provided with respectively, left side external screw thread and right external screw thread are revolved to opposite, and left side slider (17) and right slider (18) are the screw set respectively and are established in dwang (19) outside left side half regional and right half regional, and dwang (19) left end passes the left rotation hole and is connected with motor (20) right part output, and dwang (19) right-hand member inserts to rotate right downtheholely, mount pad (21) bottom and bottom plate (1) top left side half regional connection, mount pad (21) top and motor (20) bottom are connected.

2. The testing jig according to claim 1, further comprising a left stabilizer bar (22) and a right stabilizer bar (23), wherein the left slider (17) and the right slider (18) are laterally provided with a left through hole and a right through hole in the left sidewall upper half area, respectively, the left stabilizer bar (22) and the right stabilizer bar (23) are connected to the left sidewall central area in the left sliding groove and the right sliding groove at the left end, respectively, and the left stabilizer bar (22) and the right stabilizer bar (23) are connected to the right sidewall central area in the left sliding groove and the right sliding groove through the left through hole and the right through hole, respectively.

3. The testing jig according to claim 2, further comprising a first right stabilizer plate (24), a second right stabilizer plate (25) and a right slide bar (26), wherein the testing board (12) is longitudinally provided with a right through hole at the right rear side of the top end, the rear ends of the first right stabilizer plate (24) and the second right stabilizer plate (25) are respectively connected with the right half region of the front side wall of the supporting plate (7), the top end of the right slide bar (26) is connected with the central region of the bottom end of the first right stabilizer plate (24), and the bottom end of the right slide bar (26) passes through the right through hole and is connected with the central region of the top end of the second right stabilizer plate (25).

4. A test rack according to claim 3, characterized in that it further comprises a fixing rod (27) and a pull rod (28), the bottom end of the fixing rod (27) is connected with the central region of the top end of the pressure plate (11), and the left end of the pull rod (28) is connected with the upper half region of the right side wall of the fixing rod (27).

5. A test rack according to claim 4, characterized in that a first left ball bearing (29) and a first right ball bearing (30) are arranged between the turning rod (19) and the inner side walls of the left turning hole and the right turning hole, respectively.

6. A test rack according to claim 5, characterized in that it further comprises an auxiliary plate (31), the bottom end of the auxiliary plate (31) is connected with the central area of the top end of the bottom plate (1), the upper half area of the left side wall of the auxiliary plate (31) is transversely provided with a communication hole, and the rotating rod (19) passes through the communication hole and is provided with a second ball bearing (32) between the inner side wall of the communication hole.

7. A test rack according to claim 6, characterized in that the left anti-skid pad (33) and the right anti-skid pad (34) are respectively arranged on the right side wall of the left clamping plate (5) and the upper half area of the left side wall of the right clamping plate (6).

8. The test rack according to claim 7, further comprising four sets of legs (35) and four sets of rollers (36), wherein the top ends of the four sets of legs (35) are respectively connected with the left front side, the right front side, the left rear side and the right rear side of the bottom end of the base plate (1), and the four sets of rollers (36) are respectively rotatably mounted at the bottom ends of the four sets of legs (35).