CN205950504U - On - line measuring device of precision roll shape - Google Patents
On - line measuring device of precision roll shape Download PDFInfo
- Publication number
- CN205950504U CN205950504U CN201620954573.2U CN201620954573U CN205950504U CN 205950504 U CN205950504 U CN 205950504U CN 201620954573 U CN201620954573 U CN 201620954573U CN 205950504 U CN205950504 U CN 205950504U
- Authority
- CN
- China
- Prior art keywords
- measurement
- roll
- line
- arm
- bar
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Landscapes
- Constituent Portions Of Griding Lathes, Driving, Sensing And Control (AREA)
- Grinding Of Cylindrical And Plane Surfaces (AREA)
Abstract
The utility model discloses an on - line measuring device of precision roll shape, roll grinder axial slide orientation can be followed in the roll grinder frame to the measurement bay, the motion of drive arrangement drive measurement bay, the gage beam is installed on the measurement bay, the roll that roll grinder went up online processing can kept away from and be close to to gage beam one end, the motion of the 2nd drive arrangement drive gage beam, three piece at least measuring sticks are installed in gage beam one end, install displacement sensor on three measuring sticks respectively, just can distribute the respectively outside of on the same radial section of online processing roll three direction of displacement sensor on three measuring sticks, and each displacement sensor can sense it respectively to the surperficial perpendicular distance of the roll of online processing and deliver a letter in roll grinder's control system, the utility model discloses roll grinding state to the grinding in -process carries out real -time detection, and the grinding is efficient, and measurement accuracy and measurement of efficiency are high, the no fish tail in breaker roll surface.
Description
Technical field
This utility model is related to a kind of roller surface process equipment, particularly to a kind of on-line measurement of finishing roller shape
Device.
Background technology
Roll is the key tool of metal rolled molding, and the degree of accuracy of roll profile and high-quality roller surface are to ensure that
Basic demand in metal mill product forming process.At present, predominantly 2 points of the on-line measurement mode that roll grinder adopts connects
Touch measurement apparatus, however, there is following inherent defect in two-point contact formula measurement：
1) two-point measurement cannot obtain isolating the roll profile error after the radial motion error of support level, thus cannot
Obtain real roll profile error, impact is follow-up to roll machining accuracy；
2) in measurement process, for any shape containing odd number salient angle, the traditional circle measured by two point method measuring instrument
Degree will be all proper circle it is impossible to obtain real roll profile；
3) the ceramic measurement head in contact type measurement the high-accuracy roller surface after the completion of grinding can be caused scratch it is impossible to
Meet the requirement to high accuracy roll for the high-end customer.
Utility model content
In order to make up above deficiency, this utility model provides a kind of on-line measurement device of finishing roller shape, this essence
The on-line measurement device of close roll shape can obtain the real conditions of roller diameter and roller shape with real-time online, and will not be to mill
Cut high accuracy roller surface to cause to scratch.
This utility model be employed technical scheme comprise that to solve its technical problem：A kind of finishing roller shape online
Measurement apparatus, including measurement bay, measurement arm, measurement bar, first driving means, the second driving means and roll grinder control system
System, described measurement bay can slide axially along roll grinder and be positioned in roll grinder frame, and first driving means drive measurement
Frame moves, and measurement arm is installed on measurement bay, measurement arm one end can away from the roll with on-line machining on the roll grinder,
Second driving means drive measurement arm motion, and at least three measurement bars are installed on measurement arm one end, three measurement bars are pacified respectively
Equipped with displacement transducer, the displacement transducer in three measurement bars be able to be distributed in the same radial cut of on-line machining roll respectively
The outside in three directions on face, and each displacement transducer is able to sense that it arrives the vertical of the roller surface of on-line machining
Distance is simultaneously messaging in the control system of roll grinder.
As further improvement of the utility model, described first driving means are the saddle of roll grinder, measurement bay
It is fixedly installed on saddle.
As further improvement of the utility model, institute's displacement sensors are laser displacement sensor.
As further improvement of the utility model, described measurement arm one end can be away from online with roll grinder
The structure of roll of processing is：The measurement arm other end can be positioned on measurement bay around the axis of rotation parallel with roll axis,
Second driving means drive measurement arm to rotate around the shaft.
As further improvement of the utility model, described second driving means are electric pushrod or hydraulic cylinder, and it is fixed
End is articulated with measurement bay, and its tache motorice is articulated with measurement arm, electric pushrod or hydraulic cylinder, measurement bay and measurement arm three it
Between formed triangular structure.
As further improvement of the utility model, described electric pushrod or hydraulic cylinder are provided with upper and lower stopping means,
Upper and lower stopping means can limit electric pushrod or the scope of hydraulic cylinder end motion.
As further improvement of the utility model, described measurement bar includes first, second and third measurement bar, and wherein first and second
Measurement bar is symmetrically distributed in the 3rd measurement bar both sides, and first and second measurement bar can be slidingly positioned on measurement arm one end relatively,
3rd measurement bar can be slidingly positioned on measurement arm one end along the direction of the vertical first and second measurement bar direction of motion, and first and second
The axis of line on-line machining roll just on roll grinder of the upper displacement sensor of measurement bar, be additionally provided with third and fourth, five drives
Dynamic device, this third and fourth, five driving means drive first, second and third measurement bar motion respectively.
As further improvement of the utility model, third and fourth driving means described are linear electric motors, described measurement arm
One end is provided with line slideway, and first and second measurement bar is able to slip cap on line slideway, and linear electric motors drive respectively
First and second measurement bar motion, is additionally provided with first straight line grating scale and synchronous drive device, synchronous drive device realizes first and second
Measurement bar synchronous relative motion, first straight line grating scale can measure the span of first and second measurement bar and be messaging in roll grinder
Control system, the control system of roll grinder controls linear electric motors action, described 5th driving means include servomotor and
Ball-screw, described servomotor drives the 3rd measurement bar motion by ball-screw, is additionally provided with second straight line grating scale, and second
Linear grating chi can carry out closed-loop measuring to the position of the 3rd measurement bar and be messaging in the control system of roll lathe, and roll grinds
The control system of bed controls servomotor action.
As further improvement of the utility model, described measurement bar is additionally provided with micromatic setting, each fine setting dress described
Put the position being able to the upper displacement sensor of corresponding each measurement bar of adjustment.
As further improvement of the utility model, it is additionally provided with cleaning drying device, cleaning drying device includes can adjust
The automatic wiper of compression pressure and each comprehensive nozzle of corresponding multi-pore channel in displacement transducer position, pipeline and high pressure gas
Body compressor station, on the automatic wiper of described adjustable compression pressure, Wiper blade can be to set compressive resilience tight against in roll table
On face, the comprehensive nozzle outgassing direction of described multi-pore channel is just displaced by sensor detection towards on-line machining roll on roll grinder
The surface of position, gases at high pressure compressor station passes through pipeline to multi-pore channel comprehensive nozzle conveying high-pressure gas.
Advantageous Effects of the present utility model are：This utility model can ensure in roll grinding process to roll dressing
State carries out real-time detection, and passes through control system real-time adjustment grinding process, realizes the flexibility of Roller Machining system, simultaneously
Grinding efficiency can also greatly be heightened, the measuring system of bikini can achieve Error Separation Technique (Error
Separation Technique), roll profile and the reference support position error of itself can be carried out separating, can avoid by grinding
Roll profile error caused by bed error it is ensured that the high-precision grinding of roll grinder, using the Laser Measuring in non-contact measurement
Amount head greatly improves certainty of measurement and measurement efficiency, also the high-accuracy roller surface after the completion of grinding will not be caused simultaneously
Scratch, high-end user can be met the high-quality of roll surface is required.
Brief description
Fig. 1 is the schematic diagram of measuring system structure of the present utility model；
Fig. 2 is measuring system motion schematic diagram of the present utility model.
Specific embodiment
Embodiment：A kind of on-line measurement device of finishing roller shape, including measurement bay 9, measurement arm 2, measurement bar, first
The control system of driving means 10, the second driving means 1 and roll grinder, described measurement bay 9 can be axially sliding along roll grinder
Move and be positioned in roll grinder frame, first driving means 10 drive measurement bay 9 to move, measurement arm 2 is installed on measurement bay 9,
Measurement arm 2 one end can be away from the roll with on-line machining on roll grinder, and the second driving means 1 drive measurement arm 2 to transport
Dynamic, at least three measurement bars are installed on measurement arm 2 one end, and three measurement bars are separately installed with displacement transducer 4, three measurements
Displacement transducer 4 on bar be able to be distributed in the outside in three directions on the same radial section of on-line machining roll respectively, and
Each displacement transducer 4 is able to sense the vertical dimension of its roller surface to on-line machining and be messaging in roll grinder
Control system.
When needing measurement, the second driving means 1 drive measurement arm 2 to make roll on roll grinder for its one end, measurement
Measurement bar on arm 2 one end is just distributed in the outside in three directions on the same radial section of line processing roll, first driving means
10 drive measurement bay 9 to move axially along roll grinder, realize the measurement in roll total length, during measurement, displacement transducer 4 will gather
Data be transferred to process roll grinder control system carry out operational analysis, foundation《Roundness measurement three measuring point method and its instrument
Accuracy assessment》Described in (JB/T 5996-1992), algorithm is processed, thus isolating roll profile error and support level
Error.And then in grinding process, accurately can be come and gone according to the position on the rotational angle of roller and its place guide rail, emery wheel
Movement carries out grinding, the error of roll support position is compensated, the movement of emery wheel carries out SERVO CONTROL by control system, with this
The high-precision intelligent realizing roll grinder controls grinding.
Described first driving means 10 are the saddle of roll grinder, and measurement bay 9 is fixedly installed on saddle, using watching
The mode taking motor+ball-screw drives saddle to move along roll axis direction, is driven by the saddle in roll grinder
Measurement bay 9 slides axially along roll grinder it is ensured that measurement apparatus complete to measure in roll total length, and it takes full advantage of grinding machine
The space of saddle, save energy, driving means can also be separately provided, such as single motor and ball-screw vice mechanism are come in fact
Existing.
Institute's displacement sensors 4 are laser displacement sensor 4, and described laser displacement sensor 4 is scattered reflection type laser
Sensor, certainty of measurement up to 0.2um, in laser displacement sensor 4 measurement process not with roll directly contact, it is to avoid measurement head
Damage to roller surface in measurement process.When roll rolls or saddle moves along roll axis, the change of roll profile
Change and will cause the change of laser displacement sensor 4 reading, data collecting system is by the number of Real-time Collection laser displacement sensor 4
Value, except of course that laser displacement sensor 4 can also be using other displacement transducers 4.
Described measurement arm 2 one end away from the structure with the roll of on-line machining on roll grinder can be：Measurement arm 2
The other end can be positioned on measurement bay 9 around the axis of rotation parallel with roll axis, and the second driving means 1 drive measurement arm 2
Rotate around the shaft, rotate so as to one end radially wobbles along roll by measuring arm 2, during measurement, it, near roll, measures after terminating
Then away from roll, it is to avoid interfere with devices such as Roller Machining, except being realized by hinged flip-flop movement or surveying
Amount arm 2 can be slidingly positioned on measurement bay 9 along roll grinder long roll radial alignment, drives its straight line to slide by driving means
Move and can achieve that it is close and realizes measurement and avoidance away from roll, or by the horizontal rotating shaft of vertical roller axis direction in fact
Now measure arm 2 swing, to realize measure arm 2 one end near and away from roll.
Described second driving means 1 are electric pushrod or hydraulic cylinder, and its fixing end is articulated with measurement bay 9, its tache motorice
It is articulated with measurement arm 2, between electric pushrod or hydraulic cylinder, measurement bay 9 and measurement arm 2 three, form triangular structure, electronic
Push rod or Hydraulic Cylinder measurement arm 2 make gyration around its centre of gyration, can complete measurement head and receive in measurement working position, measurement
Play the exchange campaign of position.
Described electric pushrod or hydraulic cylinder are provided with upper and lower stopping means, and upper and lower stopping means can limit electric pushrod
Or the scope of hydraulic cylinder end motion, limit electric pushrod or hydraulic cylinder end motion scope by upper and lower stopping means,
And then control measurement arm 2 amplitude of fluctuation, it is to avoid displacement transducer 4 of wounding, and ensure the accurate of measurement position, can also be in measurement
One positive stop is arranged on frame 9, this positive stop backstop is in the measurement roll side table towards on-line machining on roll grinder for the arm 2
Face, realizes the accurate restriction that measurement arm 2 is in position during measuring state.
Described measurement bar includes first, second and third measurement bar 3,8,5, and wherein first and second measurement bar 3,8 is symmetrically distributed in
Three measurement bar 5 both sides, and first and second measurement bar 3,8 can measure on arm 2 one end with respect to be slidingly positioned in, the 3rd measurement bar 5 energy
Enough directions along vertical first and second measurement bar 3,8 directions of motion are slidingly positioned on measurement arm 2 one end, first and second measurement bar 3,
The axis of line on-line machining roll just on roll grinder of 8 upper displacement sensors 4, be additionally provided with third and fourth, five drive dress
Put, this third and fourth, five driving means drive first, second and third measurement bar 3,8,5 to move, by first, second and third measurement bar respectively
3rd, 8,5 motion can adjust the distance away from the surface of roll for the displacement transducer 4, makes displacement transducer 4 be in optimal survey all the time
In the range of amount.
Third and fourth driving means described are linear electric motors, and described measurement arm 2 one end is provided with line slideway, and first and second
Measurement bar 3,8 is able to slip cap on line slideway, and linear electric motors drive first and second measurement bar 3,8 to move respectively, also
It is provided with first straight line grating scale and synchronous drive device, synchronous drive device realizes first and second measurement bar 3,8 synchronous relative motions
(synchronously open or close), first straight line grating scale can measure the span of first and second measurement bar 3,8 and be messaging in roll grinder
Control system, the control system of roll grinder controls linear electric motors action, described 5th driving means 7 include servomotor and
Ball-screw, described servomotor drives the 3rd measurement bar 5 to move by ball-screw, is additionally provided with second straight line grating scale, the
Two linear grating chis the position of the 3rd measurement bar 5 can be carried out closed-loop measuring and be messaging in roll lathe control system (logical
Cross second straight line grating scale and closed loop control carried out to the 3rd measurement bar 5 position), the control system of roll grinder controls servomotor
Action.
Micromatic setting 6 is additionally provided with described measurement bar, each micromatic setting 6 described is able to corresponding each measurement of adjustment
The position of the upper displacement sensor of bar 4, micromatic setting 6 is realized each displacement transducer 4 and is carried out position along three mutually perpendicular directions
Adjustment, can eliminate, by micromatic setting 6, the alignment error that part's machining errors cause it is ensured that three laser displacement sensors 4
In the same Normal plane of roll, and ensure the transmitting laser of three laser displacement sensors 4 all by the axial line of roll.
Be additionally provided with cleaning drying device, cleaning drying device include the automatic wiper of adjustable compression pressure and each
The comprehensive nozzle of the corresponding multi-pore channel in displacement transducer 4 position, pipeline and gases at high pressure compressor station, described adjustable compression pressure
Automatic wiper on Wiper blade can with set compressive resilience (be realized by disc spring) tight against on roller surface, described many
Duct comprehensive nozzle outgassing direction is just displaced by the table of sensor 4 test position towards on-line machining roll on roll grinder
Face, gases at high pressure compressor station passes through pipeline to multi-pore channel comprehensive nozzle conveying high-pressure gas, and automatic wiper is good by sealing
Good Wiper blade is pressed on roll, by the rotation of roll, most of grinding fluid is scraped off roller measure region, displacement transducer 4
Side is respectively mounted the comprehensive nozzle of multi-pore channel it is ensured that being cleaned doing to the grinding fluid of roller surface minority attachment in measurement process
Dry, it is to avoid the impact to displacement transducer 4 reading of roll dressing liquid and impurity.
Claims (10)
1. a kind of on-line measurement device of finishing roller shape, including measurement bay (9), measurement arm (2), measurement bar, the first driving
The control system of device (10), the second driving means (1) and roll grinder, described measurement bay can slide axially along roll grinder
It is positioned in roll grinder frame, first driving means drive measurement bay motion, and measurement arm is installed on measurement bay, measures arm one
End can be away from the roll with on-line machining on roll grinder, and the second driving means drive measurement arm to move, at least three
Measurement bar is installed on measurement arm one end, and three measurement bars are separately installed with displacement transducer (4), the displacement in three measurement bars
Sensor be able to be distributed in the outside in three directions on the same radial section of on-line machining roll respectively, and each displacement sensing
Device is able to the control system sensing the vertical dimension of its roller surface to on-line machining and being messaging in roll grinder.
2. the on-line measurement device of finishing roller shape according to claim 1, is characterized in that：Described first driving means
For the saddle of roll grinder, measurement bay is fixedly installed on saddle.
3. the on-line measurement device of finishing roller shape according to claim 1, is characterized in that：Institute's displacement sensors are
Laser displacement sensor.
4. the on-line measurement device of finishing roller shape according to claim 1, is characterized in that：Described measurement arm one end energy
Away from the structure with the roll of on-line machining on roll grinder it is enough：The measurement arm other end can be around parallel with roll axis
Axis of rotation be positioned on measurement bay, second driving means drive measurement arm rotate around the shaft.
5. the on-line measurement device of finishing roller shape according to claim 4, is characterized in that：Described second driving means
For electric pushrod or hydraulic cylinder, its fixing end is articulated with measurement bay, and its tache motorice is articulated with measurement arm, electric pushrod or liquid
Form triangular structure between cylinder pressure, measurement bay and measurement arm three.
6. the on-line measurement device of finishing roller shape according to claim 5, is characterized in that：Described electric pushrod or liquid
Cylinder pressure is provided with upper and lower stopping means, and upper and lower stopping means can limit electric pushrod or the model of hydraulic cylinder end motion
Enclose.
7. the on-line measurement device of finishing roller shape according to claim 1, is characterized in that：Described measurement bar includes
First, two, three measurement bars (3,8,5), wherein first and second measurement bar is symmetrically distributed in the 3rd measurement bar both sides, and first and second measurement
Bar can be slidingly positioned on measurement arm one end relatively, and the 3rd measurement bar can be along the vertical first and second measurement bar direction of motion
Direction is slidingly positioned on measurement arm one end, the line of the upper displacement sensor of first and second measurement bar just on roll grinder
The axis of line processing roll, be additionally provided with third and fourth, five driving means, this third and fourth, five driving means drive first respectively,
2nd, three measurement bar motion.
8. the on-line measurement device of finishing roller shape according to claim 7, is characterized in that：Third and fourth driving described
Device is linear electric motors, and described measurement arm one end is provided with line slideway, first and second measurement bar be able to slip cap located at
On line slideway, linear electric motors drive first and second measurement bar motion respectively, be additionally provided with first straight line grating scale and synchronous driving fills
Put, synchronous drive device realizes first and second measurement bar synchronous relative motion, first straight line grating scale can measure first and second survey
The span of gauge rod is simultaneously messaging in the control system of roll grinder, and the control system of roll grinder controls linear electric motors action, described
5th driving means (7) include servomotor and ball-screw, and described servomotor drives the 3rd measurement bar by ball-screw
Motion, is additionally provided with second straight line grating scale, second straight line grating scale can carry out closed-loop measuring simultaneously to the position of the 3rd measurement bar
It is messaging in the control system of roll lathe, the control system of roll grinder controls servomotor action.
9. the on-line measurement device of finishing roller shape according to claim 1, is characterized in that：Also set in described measurement bar
There is micromatic setting (6), each micromatic setting described is able to the position of the upper displacement sensor of corresponding each measurement bar of adjustment.
10. the on-line measurement device of finishing roller shape according to claim 1, is characterized in that：It is additionally provided with cleaning drying
Device, the automatic wiper that cleaning drying device includes adjustable compression pressure is corresponding many with each displacement transducer position
The comprehensive nozzle in duct, pipeline and gases at high pressure compressor station, Wiper blade energy on the automatic wiper of described adjustable compression pressure
Enough to set compressive resilience tight against on roller surface, the comprehensive nozzle outgassing direction of described multi-pore channel is just towards on roll grinder
On-line machining roll is displaced by the surface of sensor test position, and gases at high pressure compressor station passes through pipeline to the comprehensive spray of multi-pore channel
Mouth conveying high-pressure gas.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201620954573.2U CN205950504U (en) | 2016-08-26 | 2016-08-26 | On - line measuring device of precision roll shape |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201620954573.2U CN205950504U (en) | 2016-08-26 | 2016-08-26 | On - line measuring device of precision roll shape |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN205950504U true CN205950504U (en) | 2017-02-15 |
Family
ID=57980903
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201620954573.2U Active CN205950504U (en) | 2016-08-26 | 2016-08-26 | On - line measuring device of precision roll shape |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN205950504U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106141917A (en) * | 2016-08-26 | 2016-11-23 | 昆山华辰重机有限公司 | The on-line measurement device of finishing roller shape |
-
2016
- 2016-08-26 CN CN201620954573.2U patent/CN205950504U/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106141917A (en) * | 2016-08-26 | 2016-11-23 | 昆山华辰重机有限公司 | The on-line measurement device of finishing roller shape |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN106141917A (en) | The on-line measurement device of finishing roller shape | |
| CN102059650B (en) | Precise on-site measuring device and measuring method for sphericity of spherical surface | |
| CN201221938Y (en) | Non-contact intelligent off-line testing instrument of large-scale cylinder workpiece | |
| CN107084673A (en) | A kind of the measurement detection means and detection method of motor vehicle wheels external diameter and internal diameter | |
| CN202101656U (en) | Double-measuring head structure | |
| CN108278979A (en) | A kind of blade situ contact formula three-dimensional measuring apparatus and method | |
| CN103822605B (en) | Splicing measuring device of optical elements of large caliber profile | |
| CN100584533C (en) | Follow measuring method of crankshaft connecting rod roundness | |
| CN102506678A (en) | Position detecting system for edge of winding-up H-shaped wheel of wire drawing machine and control method thereof | |
| CN102672612B (en) | Workpiece device for on-line measuring of numerical control roll grinder | |
| CN105241392B (en) | The full surface three dimension measuring apparatus and its measuring method of a kind of complicated columnar workpiece | |
| CN102198634B (en) | Measuring method and device for in process measurement on crank shaft contour | |
| CN109827538B (en) | Bar flatness detection device and flatness detection method thereof | |
| CN204725322U (en) | A kind of plate size detection machine | |
| CN206656700U (en) | The two-in-one detection machine of height diameter | |
| CN106938442A (en) | A kind of numerical control grinding test machine | |
| CN102059651A (en) | Roundness measurement method for bent axle follow-up grinding | |
| CN101187538A (en) | Screw gauge detection method | |
| CN205950504U (en) | On - line measuring device of precision roll shape | |
| CN106123757A (en) | A kind of bent axle many gauge heads follow-up detector | |
| CN203534551U (en) | Compressor rotor detection apparatus | |
| CN112525117A (en) | Thickness measuring system for high-temperature cast pipe online and use method thereof | |
| CN103447957A (en) | Method for measuring initial positions of grinding wheel of numerical control grinder and dressing roller | |
| KR20140006572A (en) | Large pipe length and straightness measuring device | |
| CN103182680A (en) | Dynamic online measuring device and method for ball screw grinding |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CP01 | Change in the name or title of a patent holder |
Address after: 215337, Jiangsu Province, Suzhou City, Kunshan Province Zhou Town, Long Jing Jing Road No. 333 Patentee after: Huachen precision equipment (Kunshan) Limited by Share Ltd Address before: 215337, Jiangsu Province, Suzhou City, Kunshan Province Zhou Town, Long Jing Jing Road No. 333 Patentee before: Kunshan Huachen Heavy Machinery Co., Ltd. |
|
| CP01 | Change in the name or title of a patent holder |