Antenna test and calibration clamp
By designing antenna testing and calibration fixtures, the precise position adjustment of the antenna in three-dimensional space is achieved using longitudinal and horizontal driving devices, which solves the problem of inaccurate antenna position adjustment in traditional testing methods, and improves the stability and testing of high-precision navigation systems Data accuracy.
Patent Information
- Application Number
- CN202323429498.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-15
- Publication Date
- 2025-01-10
- Estimated Expiration
- 2033-12-15
AI Technical Summary
Traditional antenna testing methods cannot accurately adjust the antenna position, resulting in rough phase center offset estimation, increasing measurement errors, especially on antennas of different shapes, making it difficult to ensure the stability of high-precision navigation systems.
An antenna testing and calibration fixture is designed, including a longitudinal drive device, a first horizontal drive device and a second horizontal drive device, through which the precise adjustment of the antenna support platform in the three-dimensional space is achieved, ensuring that the antenna is located in the arc where the probe is located. Center, independently adjust the X, Y, and Z directions to reduce measurement errors.
It realizes the precise position adjustment of the antenna in three-dimensional space, reduces measurement errors, and is suitable for antennas of various specifications and types, ensuring the stability of high-precision navigation systems and the accuracy of test data.
Smart Images
Figure CN222337216U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the field of antenna testing, in particular to an antenna testing and calibration fixture. Background Art
[0002] The high-precision antennas of current high-precision satellite navigation system terminal receivers all require very stable phase centers. Accurate calibration of the antenna phase center is crucial to ensure the high accuracy of the navigation system. Traditional testing methods have the problem that the antenna is simply fixed and the antenna position cannot be accurately adjusted, especially for antennas of different shapes. This leads to a rough estimate of the antenna phase center offset. At the same time, the movement in the XY direction will affect each other, increasing the measurement error and making calibration more challenging. The urgent need to solve this problem has driven the search for new calibration methods to ensure the stability and high performance of antennas in high-demand environments. Utility Model Content
[0003] In order to overcome the above-mentioned defects, the utility model provides an antenna testing and calibration fixture, which can ensure that the antenna is located at the center of the arc where the probe is located, ensure the accuracy of the test data, and further ensure that the antenna of the high-precision navigation system exhibits stable and reliable characteristics.
[0004] The utility model adopts a technical solution to solve the technical problem: an antenna test and calibration fixture, including an antenna support platform, a base, a lifting column, a measured object bracket, a longitudinal drive device, a first horizontal drive device, a second horizontal drive device, a measured object displacement acquisition device and a correction calculation system, assuming that the Z direction is a vertical direction, and the X direction and the Y direction are two mutually perpendicular directions on a horizontal plane, the base can be fixedly installed on the holding pole of the antenna test system, the lifting column can be installed on the base in a manner that it can move along the Z direction, the longitudinal drive device drives the lifting column to move, the fixed end of the first horizontal drive device is fixedly installed on the lifting column, the moving end of the first horizontal drive device can slide linearly along the X direction on the horizontal plane, and the fixed end of the second horizontal drive device The end is fixedly installed on the moving end of the first horizontal driving device, the moving end of the second horizontal driving device can slide linearly in the Y direction on the horizontal plane, the antenna support platform is fixedly installed on the moving end of the second horizontal driving device, the object support is installed on the antenna support platform, the object support can fix and position the object to be tested, the object displacement acquisition device can collect the displacement data of the antenna support platform in the Z direction, the X direction and the Y direction, the correction calculation system communicates and transmits with the object displacement acquisition device and obtains the object displacement data, the correction calculation system electronically communicates with the test data output module of the antenna test system, and the correction calculation system can calculate the antenna phase center offset according to the displacement data of the object to be tested and the test data of the antenna test system.
[0005] As a further improvement of the present utility model, the first horizontal drive device and the second horizontal drive device both include a horizontal bracket, a linear guide rail, a screw nut slider mechanism and a rotation drive device, the linear guide rail is fixedly mounted on the horizontal bracket, the screw of the screw nut slider mechanism can be rotatably mounted on the horizontal bracket, the nut slider of the screw nut slider mechanism is stopped in the circumferential direction and can be slid in the axial direction on the linear guide rail, the rotation drive device drives the screw of the screw nut slider mechanism to rotate, the horizontal bracket of the first horizontal drive device is fixedly mounted on the lifting column, the horizontal bracket of the second horizontal drive device is fixedly mounted on the nut slider of the screw nut slider of the first horizontal drive device, and the antenna support platform is fixedly mounted on the nut slider of the screw nut slider of the second horizontal drive device.
[0006] As a further improvement of the present utility model, the rotation driving devices of the first horizontal driving device and the second horizontal driving device are knobs, and the knobs are coaxially fixedly connected to the screw of the screw nut slider mechanism.
[0007] As a further improvement of the present invention, the device for acquiring the displacement of the object to be measured includes a longitudinal scale arranged on the lifting column and a horizontal scale arranged on the horizontal bracket of the first horizontal drive device and the second horizontal drive device. The longitudinal scale on the longitudinal scale can be read directly opposite to the side surface of the base, the horizontal scale on the horizontal scale on the first horizontal drive device can be read directly opposite to the side wall of the nut slider on the first horizontal drive device, and the horizontal scale on the horizontal scale on the second horizontal drive device can be read directly opposite to the side wall of the nut slider on the second horizontal drive device.
[0008] As a further improvement of the present invention, the longitudinal drive device includes a gear, a rack, a handle and a closing lock. The rack extending in the vertical direction is fixedly mounted on the lifting column, and the gear can be rotatably mounted on the base around a rotating shaft extending in the horizontal direction. The handle is coaxially fixedly connected to the gear, and the gear and the rack are meshed for transmission. The closing lock can fix the gear or the rack and the base at any position.
[0009] As a further improvement of the present invention, the closing lock is a locking screw movably threadedly connected to the base, and the end of the locking screw can be tightly pressed against the outer circumferential surface of the gear shaft.
[0010] As a further improvement of the present utility model, the base is provided with a guide channel with a non-circular cross-section, the cross-section of the lifting column is a non-circular structure consistent with the cross-section of the guide channel, the lifting column can slide longitudinally and be inserted in the guide channel, and the base is also provided with a gear positioning frame with an inverted U-shaped structure, the gear can be rotatably accommodated in the gear positioning frame, the rotating shaft of the gear can be rotatably inserted on the two side walls of the gear positioning frame, and the side wall of the guide channel on the base is provided with an opening structure connected to the inner side of the inverted U-shaped structure of the gear positioning frame, the rack fixedly mounted on the side wall of the lifting column is accommodated in the opening structure, and the circumferential outer side surface of the gear is meshed with the rack for transmission through the opening structure.
[0011] As a further improvement of the utility model, at least two object holders can be installed on the upper surface of the antenna support platform so as to slide relative to each other radially along the antenna support platform. A device for adjusting and positioning the object holders is also provided. The device for adjusting and positioning the object holders can fix and position each object holder on the antenna support platform. The object holders are provided with horizontal supporting surfaces and vertical clamping surfaces. The lower side surfaces of the object to be measured can be supported on the horizontal supporting surfaces of each object holder, and the circumferential outer side walls of the object to be measured can be tightly clamped between the vertical clamping surfaces of each object holder.
[0012] As a further improvement of the utility model, at least two linear guide grooves extending radially are provided on the upper surface of the antenna support platform, and a guide slider is provided at the lower end of each object support, and the guide slider can be inserted into the linear guide groove for linear sliding sliding.
[0013] As a further improvement of the present invention, the object support adjustment and positioning device is a screw rod installed on the antenna support platform which is axially stopped and rotatable in the circumferential direction, and the guide slider at the lower end of the object support is movably threadedly connected to the screw rod.
[0014] The beneficial effects of the utility model are as follows: the utility model drives the antenna support platform to move in a three-dimensional space within a certain range through a longitudinal drive device, a first horizontal drive device and a second horizontal drive device, thereby realizing arbitrary adjustment of the antenna position in the three-dimensional space within a certain range, so that the antenna is located at the center point of the arc where the probe of the antenna test system is located, and the movement between each axis is independent of each other, avoiding measurement errors caused by mutual interference during movement, and ensuring the accuracy of test data. At the same time, the four movable test object brackets on the support platform can be suitable for the positioning of antennas of various specifications and types. The utility model is easy to install and carry in the antenna test system, and has accurate calibration, simple operation, low error and high precision. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 It is a three-dimensional diagram of the utility model;
[0016] Figure 2 It is the front view of the utility model. DETAILED DESCRIPTION
[0017] Embodiment: An antenna test and calibration fixture, comprising an antenna support platform 1, a base 2, a lifting column 3, a test object bracket 4, a longitudinal drive device, a first horizontal drive device 5, a second horizontal drive device 6, a test object displacement acquisition device and a correction calculation system, assuming that the Z direction is a vertical direction, and the X direction and the Y direction are two mutually perpendicular directions on a horizontal plane, the base 2 can be fixedly installed on the holding pole of the antenna test system, the lifting column 3 can be installed on the base 2 to move along the Z direction, the longitudinal drive device drives the lifting column 3 to move, the fixed end of the first horizontal drive device 5 is fixedly installed on the lifting column 3, the moving end of the first horizontal drive device 5 can slide linearly along the X direction on the horizontal plane, and the fixed end of the second horizontal drive device 6 is fixedly installed on On the moving end of the first horizontal driving device 5, the moving end of the second horizontal driving device 6 can slide linearly along the Y direction on the horizontal plane, the antenna support platform 1 is fixedly installed on the moving end of the second horizontal driving device 6, the object support 4 is installed on the antenna support platform 1, the object support 4 can fix the position of the object to be measured, the object displacement acquisition device can collect the displacement data of the antenna support platform 1 in the Z direction, the X direction and the Y direction, the correction calculation system communicates and transmits with the object displacement acquisition device and obtains the object displacement data, the correction calculation system electronically communicates with the test data output module of the antenna test system, and the correction calculation system can calculate the antenna phase center offset according to the displacement data of the object to be measured and the test data of the antenna test system.
[0018] The base 2 is provided with six connection holes. When in use, the six connection holes provided on the base 2 are inserted with plastic screws and connected with the six threaded holes corresponding to them provided on the top of the holding pole. After the antenna is fixedly installed on the bracket 4 of the object to be tested, the position of the antenna is adjusted according to the center position of the arc where the probe is located marked by the cross laser of the antenna test system. The height of the lifting column 3 is adjusted by the longitudinal drive device, and the position of the antenna support platform 1 along the X direction and the Y direction on the horizontal plane is adjusted by the first horizontal drive device 5 and the second horizontal drive device 6, so as to realize the adjustment of the antenna to be tested at any position within a certain range of three-dimensional space, ensure that the antenna as the object to be tested is always kept at the center position of the arc where the probe of the antenna test system is located during the test, so as to ensure that the antenna test is accurate and stable, and the adjustment structure The structure can be adjusted according to the actual position of antennas of different specifications and types after installation to ensure the test accuracy. During the antenna test, the moving position data in three-dimensional space are obtained by the displacement acquisition device of the object under test. The correction calculation system obtains the antenna test data through electronic communication with the output module of the antenna test system. The correction calculation system generally uses a computer. The correction calculation system can accurately calculate the antenna phase center offset according to the movement distance of the test antenna along the three directions of X, Y, and Z and the test data in the test system (the computer calculates and obtains according to the existing formula). Since the movement displacement data of the antenna in the three directions of X, Y, and Z obtained by this application is accurate, the calculation data of the antenna phase center offset is accurate, and then the antenna of the high-precision navigation system is guaranteed to show stable and reliable characteristics during use. Avoid errors in the calculation of the antenna phase center offset due to inaccurate displacement data during antenna testing, which affects the antenna test data.
[0019] The first horizontal driving device 5 and the second horizontal driving device 6 both include a horizontal bracket 51, a linear guide rail, a screw nut slider mechanism and a rotation driving device. The linear guide rail is fixedly mounted on the horizontal bracket 51. The screw 52 of the screw nut slider mechanism can be rotatably mounted on the horizontal bracket 51. The nut slider 53 of the screw nut slider mechanism is stopped in the circumferential direction and can be slid in the axial direction on the linear guide rail. The rotation driving device drives the screw 52 of the screw nut slider mechanism to rotate. The horizontal bracket 51 of the first horizontal driving device 5 is fixedly mounted on the lifting column 3. The horizontal bracket 51 of the second horizontal driving device 6 is fixedly mounted on the nut slider 53 of the screw 52 nut slider 53 of the first horizontal driving device 5. The antenna support platform 1 is fixedly mounted on the nut slider 53 of the screw 52 nut slider 53 of the second horizontal driving device 6.
[0020] There are four connecting holes of the same size in the center of the antenna support platform 1. Plastic screws are passed through the connecting holes in the center of the antenna support platform 1 and connected to the screw holes on the nut slider 53 on the second horizontal drive device 6 to achieve fixed installation of the antenna support platform 1 on the nut slider 53 on the second horizontal drive device 6. The precise adjustment of the position of the antenna support platform 1 along the X and Y directions on the horizontal plane is achieved through the screw nut slider mechanism. The antenna support platform 1 can maintain its current state after moving. In order to ensure that the antenna support platform 1 does not slide during the test, a locking device is also provided to keep the screw nut slider mechanism stationary after adjustment.
[0021] The rotation drive device of the first horizontal drive device 5 and the second horizontal drive device 6 is a knob 54, and the knob 54 is coaxially fixedly connected to the screw 52 of the screw nut slider mechanism. Manual adjustment is performed by the knob 54, which has a simple structure, a small size, and is easy to carry. In addition, electric adjustment can also be performed by a servo motor.
[0022] The displacement acquisition device of the measured object includes a longitudinal scale 7 arranged on the lifting column 3 and a horizontal scale 8 arranged on the horizontal bracket 51 of the first horizontal drive device 5 and the second horizontal drive device 6. The longitudinal scale on the longitudinal scale 7 can read the reading directly opposite to the upper side of the base 2, the horizontal scale on the horizontal scale 8 on the first horizontal drive device 5 can read the reading directly opposite to the side wall of the nut slider 53 on the first horizontal drive device 5, and the horizontal scale on the horizontal scale 8 on the second horizontal drive device 6 can read the reading directly opposite to the side wall of the nut slider 53 on the second horizontal drive device 6. The moving distance of the antenna in the vertical direction and the horizontal direction, which are two mutually perpendicular directions, is read through the longitudinal scale 7 and the horizontal scale 8, and then the read data is input into the correction calculation system. Alternatively, a laser distance measuring device can be used to automatically measure the distance and automatically transmit the data to the correction calculation system.
[0023] The longitudinal drive device includes a gear 9, a rack 10, a handle 11 and a closing lock 12. The rack 10 extending in the vertical direction is fixedly installed on the lifting column 3. The gear 9 can be installed on the base 2 so as to rotate around a rotating shaft extending in the horizontal direction. The handle 11 is coaxially fixedly connected with the gear 9. The gear 9 and the rack 10 are meshed for transmission. The closing lock 12 can fix the gear 9 or the rack 10 and the base 2 at any position. The gear 9 and the rack 10 are meshed for transmission. The lifting column 3 is lifted and lowered in the longitudinal direction by rotating the gear 9 by the handle 11. The lifting column 3 does not rotate during the lifting process, which ensures the accuracy of the position and placement of the antenna on the horizontal plane and is easy to adjust. There are holes on the top of the lifting column 3 that are connected to the first horizontal drive device 5 through plastic screws.
[0024] The closing lock 12 is a locking screw that is movably threadedly connected to the base 2, and the end of the locking screw can be tightly pressed against the outer circumferential surface of the rotating shaft of the gear 9. After the locking screw is tightened, the locking screw supports the rotating shaft of the gear 9, so that the rotating shaft of the gear 9 cannot rotate, thereby fixing and positioning the lifting column 3 to prevent it from sliding down due to gravity during the test. In addition to using the locking screw to support the rotating shaft of the gear 9, a horizontal sliding plug can also be inserted into the tooth groove of the gear 9 to prevent the gear 9 from rotating, or inserted into the tooth groove of the rack 10 to prevent the rack 10 from sliding. This is an equivalent replacement that can be easily thought of by a person skilled in the art based on the present application, and it also belongs to the protection scope of the present application.
[0025] The base 2 is provided with a guide channel with a non-circular cross section, the lifting column 3 has a non-circular structure consistent with the cross section of the guide channel, the lifting column 3 can slide longitudinally and is inserted in the guide channel, the base 2 is also provided with a gear 9 positioning frame with an inverted U-shaped structure, the gear 9 can be rotatably accommodated in the gear 9 positioning frame, the rotating shaft of the gear 9 can be rotatably inserted on the two side walls of the gear 9 positioning frame, the side wall of the guide channel on the base 2 is provided with an opening structure connected to the inner side of the inverted U-shaped structure of the gear 9 positioning frame, the rack 10 fixedly installed on the side wall of the lifting column 3 is accommodated in the opening structure, and the circumferential outer side of the gear 9 is meshed and transmitted with the rack 10 through the opening structure. The lifting column 3 with a square column structure slides up and down in the square guide channel, further avoiding the lifting column 3 from rotating during the lifting process, and ensuring the accurate placement of the antenna on the horizontal plane.
[0026] At least two object holders 4 can be installed on the upper surface of the antenna support platform 1 so as to slide relative to each other along the radial direction of the antenna support platform 1. An object holder adjustment and positioning device 13 is also provided. The object holder adjustment and positioning device 13 can fix and position each object holder 4 on the antenna support platform 1. The object holders 4 are provided with horizontal holding surfaces 41 and vertical clamping surfaces 42. The lower surface of the object can be held on the horizontal holding surfaces 41 of each object holder 4, and the outer circumferential wall of the object can be tightly clamped between the vertical clamping surfaces 42 of each object holder 4. By using an object holder 4 that can move forward and backward, the size of the support space can be adjusted according to the size and type of the object.
[0027] At least two linear guide grooves 14 extending in the radial direction are provided on the upper surface of the antenna support platform 1, and a guide slider 43 is provided at the lower end of each object support 4, and the guide slider 43 can be inserted into the linear guide groove 14 in a linear sliding manner. The guide slider 43 on the object support 4 slides linearly along the linear guide groove 14 on the antenna support platform 1, thereby realizing the radial forward and backward translation of the object support 4 on the antenna support platform 1.
[0028] The object support adjustment and positioning device 13 is a screw rod installed on the antenna support platform 1, which is axially fixed and circumferentially rotatable. The guide slider 43 at the lower end of the object support 4 is movably screwed to the screw rod. The position of the object support 4 is adjusted by rotating the screw rod, and the object can maintain the current position after adjustment.
[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. An antenna testing and calibration fixture, characterized in that: The invention comprises an antenna support platform (1), a base (2), a lifting column (3), a measured object support (4), a longitudinal driving device, a first horizontal driving device (5), a second horizontal driving device (6), a measured object displacement acquisition device and a correction calculation system, wherein the Z direction is a vertical direction, the X direction and the Y direction are two mutually perpendicular directions on a horizontal plane, the base can be fixedly mounted on a holding pole of an antenna test system, the lifting column can be mounted on the base so as to move along the Z direction, the longitudinal driving device drives the lifting column to move, the fixed end of the first horizontal driving device is fixedly mounted on the lifting column, the moving end of the first horizontal driving device can slide linearly along the X direction on the horizontal plane, the fixed end of the second horizontal driving device is fixedly mounted on the moving end of the first horizontal driving device, the moving end of the second horizontal driving device can slide linearly along the Y direction on the horizontal plane, the antenna support platform is fixedly mounted on the moving end of the second horizontal driving device, the measured object support is mounted on the antenna support platform, the measured object support can be fixedly mounted on the lifting column, the moving end of the first horizontal driving device can slide linearly along the Y direction on the horizontal plane, the antenna support platform is fixedly mounted on the moving end of the second horizontal driving device, the measured object support is mounted on the antenna support platform, The object to be measured is positioned, the displacement acquisition device of the object to be measured can collect the displacement data of the antenna support platform in the Z direction, the X direction and the Y direction, the correction calculation system communicates with the displacement acquisition device of the object to be measured and obtains the displacement data of the object to be measured, the correction calculation system electronically communicates with the test data output module of the antenna test system, and the correction calculation system can calculate the antenna phase center offset according to the displacement data of the object to be measured and the test data of the antenna test system. The longitudinal drive device comprises a gear (9), a rack (10), a handle (11) and a closing lock (12), the rack extending in the vertical direction is fixedly installed on the lifting column, the gear can be rotatably installed on the base around a rotating shaft extending in the horizontal direction, the handle is coaxially fixedly connected to the gear, the gear and the rack are meshed for transmission, the closing lock can fix the gear or the rack and the base at any position, the closing lock is a locking screw movably connected to the base, and the end of the locking screw can be tightly pressed against the outer circumferential surface of the gear shaft.
2. The antenna test and calibration fixture according to claim 1, characterized in that: The first horizontal drive device and the second horizontal drive device both comprise a horizontal support (51), a linear guide rail, a screw nut slider mechanism and a rotation drive device, wherein the linear guide rail is fixedly mounted on the horizontal support, the screw (52) of the screw nut slider mechanism is rotatably mounted on the horizontal support, the nut slider (53) of the screw nut slider mechanism is circumferentially fixed and axially slidably mounted on the linear guide rail, the rotation drive device drives the screw of the screw nut slider mechanism to rotate, the horizontal support of the first horizontal drive device is fixedly mounted on the lifting column, the horizontal support of the second horizontal drive device is fixedly mounted on the nut slider of the screw nut slider of the first horizontal drive device, and the antenna support platform is fixedly mounted on the nut slider of the screw nut slider of the second horizontal drive device.
3. The antenna test and calibration fixture according to claim 2, characterized in that: The rotation driving devices of the first horizontal driving device and the second horizontal driving device are knobs (54), and the knobs are coaxially fixedly connected to the screw of the screw nut slider mechanism.
4. The antenna test and calibration fixture according to claim 1 or 2, characterized in that: The device for obtaining the displacement of the object to be measured comprises a longitudinal scale (7) arranged on a lifting column and a horizontal scale (8) arranged on a horizontal bracket of a first horizontal drive device and a second horizontal drive device, wherein the longitudinal scale on the longitudinal scale can be read directly in line with the upper side surface of the base, the horizontal scale on the horizontal scale on the first horizontal drive device can be read directly in line with the side wall of a nut slider on the first horizontal drive device, and the horizontal scale on the horizontal scale on the second horizontal drive device can be read directly in line with the side wall of a nut slider on the second horizontal drive device.
5. The antenna testing and calibration fixture according to claim 1, characterized in that: The base is provided with a guide channel with a non-circular cross-section, and the cross-section of the lifting column is a non-circular structure consistent with the cross-section of the guide channel. The lifting column can slide longitudinally and be inserted in the guide channel. The base is also provided with a gear positioning frame with an inverted U-shaped structure. The gear can be rotatably accommodated in the gear positioning frame, and the rotating shaft of the gear can be rotatably inserted on the two side walls of the gear positioning frame. An opening structure that is connected to the inner side of the inverted U-shaped structure of the gear positioning frame is provided on the side wall of the guide channel on the base, and the rack fixedly installed on the side wall of the lifting column is accommodated in the opening structure, and the circumferential outer side surface of the gear is meshed with the rack for transmission through the opening structure.
6. The antenna testing and calibration fixture according to claim 1, characterized in that: At least two test object brackets are mounted on the upper surface of the antenna support platform so as to slide relative to each other along the radial direction of the antenna support platform. A test object bracket adjustment and positioning device (13) is also provided. The test object bracket adjustment and positioning device can fix and position each test object bracket on the antenna support platform. The test object brackets are each provided with a horizontal supporting surface (41) and a vertical clamping surface (42). The lower surface of the test object can be supported on the horizontal supporting surface of each test object bracket, and the circumferential outer wall of the test object can be tightly clamped between the vertical clamping surfaces of each test object bracket.
7. The antenna testing and calibration fixture according to claim 6, characterized in that: At least two linear guide grooves (14) extending in the radial direction are provided on the upper surface of the antenna support platform, and a guide slider (43) is provided at the lower end of each measured object bracket. The guide slider can be inserted into the linear guide groove in a linearly sliding manner.
8. The antenna testing and calibration fixture according to claim 7, characterized in that: The object support adjusting and positioning device is a screw rod which is axially fixed and circumferentially rotatable and is installed on the antenna support platform. The guide slider at the lower end of the object support is movably threadedly connected with the screw rod.