Embedded block expansion sleeve type positioning and locking device

Abstract

The utility model provides an embedded block expansion sleeve type positioning and locking device which comprises a front base and a rear base which are the same in structure. The front base and the rear base are respectively provided with a positioning and clamping module; the positioning and clamping module is used for tensioning, positioning and connecting an embedded block workpiece to form a hole in an inner hole tensioning manner; the front base and the rear base horizontally position and clamp the embedded block workpiece on the vertical outer side wall of the front base and the vertical outer side wall of the rear base through the positioning and clamping modules of the front base and the rear base respectively, the embedded block workpiece is horizontally erected and positioned above the plane of a machine tool workbench, and cutting machining spaces are reserved above and below the embedded block workpiece respectively. According to the utility model, the hole forming of the workpiece is accurately positioned by utilizing the radial circumferential expansion or contraction principle; the device is simple in overall structure, easy to machine and manufacture, suitable for machining of workpieces of various models, sufficient in machining space above and below the workpieces, convenient to program, low in labor intensity, high in product manufacturing precision and efficiency, low in cost and high in application value and popularization value.

Description

Technical Field

[0001] The utility model belongs to the technical field of clamping of workpieces on operation and transportation machine tools, and particularly relates to an inlaid block expansion sleeve type positioning and locking device. Background Art

[0002] Due to defects such as loose internal structure, pores, shrinkage cavities, and sand inclusions in the integrally cast manganese steel frog, its service life is relatively low, which affects the maintenance and use of turnouts. The combined manganese steel frog can overcome the deficiencies of the existing integrally cast frog, meet the requirements of railway transportation, avoid the phenomenon of overall scrapping due to partial damage, and is convenient for laying, maintenance, and repair operations on the premise of ensuring the performance of the frog and improving its service life. Parts such as the frog heart or wing rail have online interchangeability to reduce the replacement and repair costs. Therefore, with the increasing annual output of combined frogs and their occupying a certain market share, it is extremely urgent to efficiently and highly precisely machine each component of the combined frog and reduce the labor intensity of operators and the manufacturing cost of enterprises.

[0003] During the processing of the inlaid block of the existing inlaid wing rail type manganese steel combined frog, due to the non-magnetic material of austenite, a powerful electromagnetic or permanent magnetic chuck cannot be used for positioning and clamping, and only a general bolt pressing plate can be selected for clamping, resulting in problems such as errors in the positioning reference of the workpiece, insecure clamping, and inability to restrict the deformation of the workpiece. This leads to serious out-of-tolerance phenomena in the geometric dimensions and form and position tolerances of the inlaid block. At the same time, the operation of the operator is cumbersome, the labor intensity is high, the quality is not easy to guarantee, and it has a great impact on the later assembly of the entire frog.

[0004] Furthermore, when machining the outer installation surface of the inlaid block of the existing inlaid wing rail type manganese steel combined frog, the bottom surface of the inlaid block is used as the positioning reference. After machining the hole and the subsequent processes above, the inlaid block workpiece is removed, the inlaid block is flipped, and a depth gauge or height gauge is used again to level the workpiece with the bottom surface as the reference. There is a reference error during the front and back alignment, resulting in inconsistent heights at both ends of the inlaid block, and it is not easy to guarantee the form and position tolerances of the upper and lower mating surfaces of the installation surface after machining. When assembling with the standard rail of the wing rail later, excessive grinding amount or wing rail overturning occurs. Therefore, the problems caused by the existing conventional general tooling for inlaid blocks are: low alignment accuracy, long auxiliary time, difficult to guarantee product quality, and easy offset of the workpiece during processing. In view of this, the following improved technical solutions are proposed. Content of the Utility Model

[0005] The technical problem solved by the utility model: Provide an inlaid block expansion sleeve type positioning and locking device to solve the simple and efficient positioning and clamping of the inlaid block and ensure its processing quality.

[0006] The technical solution adopted by the utility model is as follows: an expansion sleeve type positioning and locking device for an inlay block, comprising a front base and a rear base with the same structure; the front base and the rear base are respectively provided with positioning and clamping modules; the positioning and clamping modules adopt the method of tightening inner holes to tighten and position the inlay block workpiece to form a hole; the front base and the rear base respectively position and clamp the inlay block workpiece horizontally on the vertical outer side walls of the front base and the rear base through their own positioning and clamping modules, and the inlay block workpiece is horizontally mounted and positioned above the plane of the machine tool worktable, and cutting processing space is respectively reserved above and below the inlay block workpiece.

[0007] In the above technical solution: the base has a horizontally arranged base bottom plate and a vertically arranged vertical plate; the base bottom plate is fixedly connected to the machine tool worktable through bolt holes and positioning blocks; the vertical plate is formed with a through hole; the through hole is used to prevent rotation and install the positioning clamping module.

[0008] In the above technical solution: the positioning clamping module is composed of two sets of locking nuts and flat washers, a set of stud-headed conical bolts and anti-rotation pins and multiple types of tension sleeves; a pin hole is formed in the middle of the stud-headed conical bolt; the anti-rotation pin is inserted and installed in the pin hole; both ends of the anti-rotation pin extend from the pin hole, and the extended end cooperates with the through-hole pin groove formed on the base vertical plate to prevent the radial rotation of the stud-headed conical bolt but does not limit the axial displacement of the stud-headed conical bolt; the stud-headed conical bolt is also formed with a cone structure in the middle The outer conical surface of the cone structure fits coaxially with the inner conical surface of the tension sleeve; the threads at both ends of the stud-headed conical bolt are respectively used to cover the flat washers and rotate to install the locking nut; the locking nut at the inner end is rotated to achieve the outward axial displacement of the stud-headed conical bolt; the stud-headed conical bolt that is axially displaced outward expands the tension sleeve through its cone structure, and is concentrically positioned and fixed to the inlaid block workpiece through the expanded tension sleeve; the locking nut at the outer end is used to limit and fix the outer end face of the inlaid block workpiece hole.

[0009] In the above technical solution, as a further improvement of the utility model: the upper surface of the base bottom plate of the base is provided with two spaced-apart parallel vertical plates; the two spaced-apart parallel vertical plates are respectively provided with through holes which are horizontally and concentrically arranged.

[0010] In the above technical solution: the through holes formed on the vertical plates of the front and rear bases are arranged at the same height.

[0011] In the above technical solution, as a further improvement of the utility model: the spaced parallel vertical plates are positioned and connected by vertical plate support blocks; the vertical plate support blocks are vertically fixed to the inner end faces of the vertical plates and the upper end faces of the base bottom plates.

[0012] In the above technical solution, as a further improvement of the present utility model: the vertical plate support block is a V-shaped structure.

[0013] In the above technical solution, as a further improvement of the present utility model: the base bottom plate and the vertical plate are of an integral structure.

[0014] In any of the foregoing technical solutions, as a further improvement of the present invention: a guiding structure is formed on the end face of the tensioning sleeve shaft.

[0015] In any of the foregoing technical solutions, as a further improvement of the present invention: the tensioning sleeve is a tensioning sleeve processed from spring steel containing manganese element.

[0016] Advantages of the present utility model compared with the prior art:

[0017] 1. By using the present utility model device, the formed holes drilled in the inlay block workpiece can be utilized to horizontally suspend and clamp the front and rear ends of the inlay block on a plane parallel to the machine tool workbench, and independent cutting spaces are left above and below the inlay block. By using a mounting surface forming tool, the upper and lower parts can be integrally processed at one time, improving the processing efficiency.

[0018] 2. The present utility model only operates by screwing the locking nut, and horizontally and quickly clamps the inlay block by using the tensioning principle to expand the formed hole of the inlay block. The operation is simple, effectively ensuring the consistency of product processing, with high alignment efficiency, reliable processing accuracy, and strong clamping force; during cutting, the workpiece is not prone to deviation, facilitating numerical control machine tool programming and processing, and the quality is reliable.

[0019] 3. The present utility model can replace the tensioning sleeve of the corresponding model according to the different hole diameters of the formed holes of the inlay block workpiece to adapt to the processing of different products, with excellent interchangeability and consistency. Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of the device of the present utility model;

[0021] Figure 2 It is a schematic exploded view of the positioning and clamping module of the present utility model;

[0022] Figure 3 It is a use state diagram of clamping the inlay block workpiece of the present utility model;

[0023] In the figure: 1 - base, 101 - base bottom plate, 1011 - bolt hole, 1012 - positioning block, 102 - vertical plate, 1021 - through hole, 103 - vertical plate support block, 2 - locking nut, 3 - flat washer, 4 - double-headed tapered bolt, 401 - pin hole, 402 - cone structure, 5 - anti-rotation stop pin, 6 - tensioning sleeve, 7 - positioning and clamping module, 8 - inlay block workpiece. Detailed Embodiments

[0024] Next, the attached drawings in the embodiments of the present utility model will be combined Figures 1 - 3, the technical solutions in the embodiments of the present utility model are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model.

[0025] (As Figure 3 shown) An inlaid block expansion sleeve type positioning and locking device, including bases 1 with the same front and rear structures. The front and rear bases 1 are respectively provided with positioning and clamping modules 7. The positioning and clamping module 7 adopts the method of expanding the inner hole to expand and concentrically position and connect the inlaid block workpiece 8 to form a hole. The front and rear bases 1 respectively horizontally suspend and clamp the inlaid block workpiece 8 through their respective positioning and clamping modules 7 on the vertical outer side walls of the front and rear bases 1, and the inlaid block workpiece 8 is horizontally erected and positioned above the machine tool workbench plane, and there are cutting processing spaces respectively above and below the inlaid block workpiece 8. It solves the problems of high-efficiency, simple and high-quality processing of the inlaid block workpiece 8.

[0026] In the above-mentioned embodiment: (As Figure 1 shown) The base 1 has a horizontally arranged base bottom plate 101 and a vertically arranged vertical plate 102. The base bottom plate 101 serves as a horizontal positioning reference, and the vertical plate 102 serves as a vertical positioning reference.

[0027] The base bottom plate 101 is fixedly connected to the machine tool workbench through bolt holes 1011 and positioning blocks 1012; the positioning blocks 1012 are adapted to the machine tool workbench to ensure the linear position identity of the front and rear bases 1.

[0028] The vertical plate 102 is provided with through holes 1021; the through holes 1021 are used for non-rotating installation of the positioning and clamping module 7, and the specific non-rotating installation method of the positioning and clamping module 7 is described later.

[0029] In the above-mentioned embodiment: (As Figure 2 shown) The positioning and clamping module 7 is composed of two sets of lock nuts 2 and flat washers 3, one set of double-headed tapered bolts 4, anti-rotation stop pins 5 and expansion sleeves 6 of multiple models. Among them, the expansion sleeves 6 of multiple models are used for matching different models of workpieces. The anti-rotation stop pin 5 is used for non-rotation of the positioning and clamping module 7. The double-headed tapered bolt 4 is used to realize the expansion function of the expansion sleeve 6. The lock nut 2 is an ordinary nut, and the flat washer 3 is used to prevent scratching, reduce local stress concentration, increase the contact area of the nut, and play an anti-loosening effect.

[0030] A pin hole 401 is formed in the middle of the double-headed conical bolt 4; the pin hole 401 is a square-rounded pin hole. Square-rounded pin holes may be more convenient to machine because the basic shape of the square hole is relatively simple, facilitating machining with standard cutting tools. At the same time, the rounded corner design can reduce stress concentration during machining, improving machining accuracy and efficiency. Square-rounded pin holes can provide more stable support during connection. Due to the restrictive effect of the square hole, the pin can maintain a stable posture within the hole, thus ensuring the accuracy and reliability of the connection.

[0031] The anti-rotation retaining pin 5 is inserted and installed in the pin hole 401; both ends of the anti-rotation retaining pin 5 extend out from the pin hole 401, and the extended ends are in pin slot fit with the through holes 1021 formed in the vertical plates 102 of the base 1. This fit is used to prevent the double-headed conical bolt 4 from rotating radially but does not restrict the axial displacement of the double-headed conical bolt 4.

[0032] A conical structure 402 is also formed in the middle of the double-headed conical bolt 4; the outer conical surface of the conical structure 402 is coaxially and tightly fitted with the inner conical surface of the expansion sleeve 6. Through the axial displacement of the conical structure 402, the expansion or contraction and reset of the expansion sleeve 6 are realized.

[0033] The threads at both ends of the double-headed conical bolt 4 are respectively used to sleeve flat washers 3 and rotate and install lock nuts 2; that is, first install the flat washers 3, and then install the lock nuts 2.

[0034] Rotating the lock nut 2 at the inner side end as shown in Figure 1 is used to realize the axial displacement of the double-headed conical bolt 4 outward; the double-headed conical bolt 4 with an outward axial displacement expands the expansion sleeve 6 through its conical structure 402, and concentrically positions and fixedly connects the inlaid block workpiece 8 through the expanded expansion sleeve 6 to form a hole. As for the lock nut 2 at the outer side end of the double-headed conical bolt 4 as shown in Figure 1 , the lock nut 2 at the outer side end of the workpiece is used to limit and fix the outer end face of the inlaid block workpiece 8 after the hole is formed, and limit and reinforce the workpiece to prevent the workpiece from displacing.

[0035] In the above embodiment, as a further improvement of the present invention: to realize the clamping and fixing of two inlaid block workpieces 8 on a set of front and rear bases 1: two vertical plates 102 are provided on the upper end surface of the base bottom plate 101 of the base 1 at intervals and in parallel; the through holes 1021 respectively formed in the two vertical plates 102 at intervals and in parallel are horizontally and concentrically arranged, that is, to ensure the same horizontal level of the two workpieces when clamping two inlaid block workpieces 8.

[0036] In the above embodiment, the through holes 1021 formed in the vertical plates 102 of the front and rear bases 1 are horizontally and equally high, that is, to ensure the horizontal clamping of each inlaid block workpiece 8.

[0037] In the above embodiments, as a further improvement of the present utility model: the vertical plates 102 spaced in parallel are positioned and connected by vertical plate support blocks 103; the rigidity and strength of the two vertical plates 102 are improved, and the vertical plates 102 are prevented from deforming. The vertical plate support blocks 103 are vertically fixedly connected to the inner end faces of the vertical plates 102 and the upper end faces of the base bottom plates 101, ensuring the verticality and horizontality of the respective structures of the bases 1.

[0038] In the above embodiments, as a further improvement embodiment of the present utility model: the vertical plate support block 103 has a V-shaped structure, providing necessary avoidance and sufficient processing space.

[0039] In the above embodiments, as a further improvement embodiment of the present utility model: the base bottom plate 101 and the vertical plate 102 are of an integral structure, improving the structural strength and having an excellent anti-deformation effect.

[0040] In any of the foregoing embodiments, as a further improvement embodiment of the present invention: a guiding structure is provided on the axial end face of the tension sleeve 6, and the guiding structure is used to facilitate the parallel introduction of the double-headed tapered bolt 4.

[0041] In any of the foregoing embodiments, as a preferred embodiment of the present invention: the tension sleeve is a tension sleeve processed from spring steel containing manganese elements. Selecting a tension sleeve product processed from spring steel containing manganese elements is beneficial to improving the hardenability of the product, increasing the anti-deformation and anti-fatigue properties.

[0042] A positioning and locking method for an inlaid block expansion sleeve type related to the present utility model uses any of the inlaid block expansion sleeve type positioning and locking devices, and includes the following steps (as shown in Figure 1 、 Figure 2 、 Figure 3 ):

[0043] Step S1: Fasten and position the front and rear bases 1 on the machine tool workbench through the bolt holes 1011 and the positioning blocks 1012 respectively.

[0044] Step S2: Select a tension sleeve 6 with a suitable model size corresponding to the hole of the inlaid block workpiece 8.

[0045] Step S3: First, sleeved the tension sleeve 6 on the conical structure 402 of the double-headed tapered bolt 4; then insert the anti-rotation stop pin 5 into the pin hole 401 of the double-headed tapered bolt 4; then insert the double-headed tapered bolt 4 into the through hole 1021 formed in the base 1, and cooperate the anti-rotation stop pin 5 with the pin groove formed in the through hole 1021 to prevent the double-headed tapered bolt 4 from rotating; finally, install a flat washer 3 and a locking nut 2 at the inner end of the double-headed tapered bolt 4.

[0046] Step S4: Hang the inlay workpiece 8 on the outside of the sleeve body of the expansion sleeve 6 through its hole-forming sleeve, and make the vertical inner side of the inlay workpiece 8 fit the vertical outer side wall of the vertical plate 102 of the base 1; pre-install a flat washer 3 and a locking nut 2 at the outer end of the double-headed tapered bolt 4 to prevent the inlay workpiece 8 from falling off or shifting.

[0047] Step S5: Tighten the inner-end locking nut 2 to cause axial displacement of the double-headed tapered bolt 4; the axially displaced double-headed tapered bolt 4 expands the expansion sleeve 6 through its tapered structure 402, and concentrically positions and fixedly connects the hole of the inlay workpiece 8 through the expanded expansion sleeve 6 until the hole of the inlay workpiece 8 is concentrically positioned and fixedly connected to the expansion sleeve 6 as a whole.

[0048] Step S6: Tighten the outer-end locking nut 2 to make the inner side of the inlay workpiece 8 fit the outer vertical side wall of the vertical plate 102 of the base 1 and limit and fix the inlay workpiece 8.

[0049] It also includes Step S7: Repeat tightening the inner and outer locking nuts 2 until the torque requirement is met. Repeating the tightening until the torque requirement is met can form a double-locking effect. This double-locking not only increases the axial pre-tightening force of the connection but also improves the anti-loosening ability of the connection. Repeating the tightening can ensure that both locking nuts reach the predetermined torque value, thereby reducing the risk of connection loosening caused by uneven tightening torque and ensuring the connection remains stable and reliable during long-term use or under harsh working conditions. Although repeating the tightening seemingly increases the installation steps, it actually simplifies the subsequent inspection and maintenance work because the stable connection reduces the frequency of regular inspection and maintenance.

[0050] It can be found from the above description that: by using the present utility model device, the inlay workpiece 8 can be horizontally suspended and clamped and positioned at both the front and rear ends on a plane parallel to the machine tool workbench by using the pre-drilled holes of the inlay workpiece 8, and independent cutting spaces are left at the upper and lower parts of the inlay workpiece 8. By using a mounting surface forming tool, the upper and lower parts of the inlay workpiece 8 can be integrally machined at one time, improving the processing efficiency.

[0051] The present utility model horizontally and quickly clamps the inlay workpiece 8 by simply screwing the locking nut 2 and using the expansion principle to expand the hole of the inlay workpiece 8. The operation is simple, effectively ensuring the consistency of the product processing of the inlay workpiece 8, with high alignment efficiency, reliable processing accuracy, and strong clamping force; during cutting, the inlay workpiece 8 is not prone to offset, facilitating numerical control machine tool programming and processing, and the quality is reliable.

[0052] The present utility model can replace the expansion sleeve 6 with a corresponding model according to the different hole diameters of the holes of the inlay workpiece 8 to adapt to the processing of different inlay workpiece 8 products, and the interchangeability and processing positioning consistency of each product are excellent.

[0053] In summary, the present utility model utilizes the principle that the axial slip of the conical surface of the conical structure 402 of the double-headed conical bolt 4 causes the radial circumferential expansion or contraction of the expansion sleeve 6 to accurately position the drilled hole of the workpiece 8 of the inlay to be processed; and uses the lock nut 2 to fasten it to completely restrict the degrees of freedom of the inlay workpiece 8. The overall structure of the device is relatively simple and easy to be processed and realized. The expansion sleeve 6 can be replaced according to the diameter of the hole of the inlay workpiece 8. This horizontal suspension clamping method of the inlay workpiece 8 can effectively reduce the interference of the cutting tool in the subsequent process on the processing of the inlay workpiece 8, and there is sufficient processing space on the upper and lower end surfaces of the workpiece, which is convenient for the operator to program, reduces the labor intensity, improves the manufacturing precision and efficiency of the product; reduces the production and manufacturing cost, and has high application value and popularization value.

[0054] It should be understood that although this specification is described according to one embodiment, this embodiment does not only include an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in this embodiment can also be appropriately arranged and combined to form other embodiments that can be understood by those skilled in the art.

[0055] The above-mentioned preferred embodiment is not used to limit the scope of implementation of the present utility model. Therefore, all equivalent changes made according to the content described in the claims of the present utility model should be included within the scope of the claims of the present utility model; it should be noted that: the components and materials used in the above-mentioned embodiments are commercially available unless otherwise specified.

Claims

1. An inlaid block expansion sleeve type positioning and locking device, characterized in that: It includes bases (1) with the same front and rear structures; positioning and clamping modules (7) are respectively provided on the front and rear bases (1); the positioning and clamping module (7) uses the method of expanding the inner hole to expand and positionally connect and inlay block workpieces (8) to form holes; the front and rear bases (1) respectively horizontally position and clamp the inlay block workpieces (8) on the vertical outer side walls of the front and rear bases (1) through their respective positioning and clamping modules (7), and the inlay block workpieces (8) are horizontally erected and positioned above the plane of the machine tool workbench, and cutting processing spaces are respectively left above and below the inlay block workpieces (8).

2. The inlaid block expansion sleeve type positioning and locking device according to claim 1, characterized in that: The base (1) has a horizontally arranged base bottom plate (101) and a vertically arranged vertical plate (102); the base bottom plate (101) is fixedly connected to the machine tool workbench through bolt holes (1011) and positioning blocks (1012); the vertical plate (102) is provided with a through hole (1021); the positioning and clamping module (7) is non-rotatably installed in the through hole (1021).

3. The inlaid block expansion sleeve type positioning and locking device according to claim 1 or 2, characterized in that: The positioning and clamping module (7) consists of two sets of lock nuts (2) and flat washers (3), one set of double-headed tapered bolts (4) and anti-rotation stop pins (5) and expansion sleeves (6) of multiple models; a pin hole (401) is made in the middle of the double-headed tapered bolt (4); the anti-rotation stop pin (5) is inserted and installed in the pin hole (401); both ends of the anti-rotation stop pin (5) extend from the pin hole (401), and the extended ends are in pin slot fit with the through hole (1021) made in the vertical plate (102) of the base (1) to prevent the double-headed tapered bolt (4) from rotating radially but not restricting the axial displacement of the double-headed tapered bolt (4); a tapered structure (402) is also made in the middle of the double-headed tapered bolt (4); the outer conical surface of the tapered structure (402) is coaxially fitted with the inner conical surface of the expansion sleeve (6); the threads at both ends of the double-headed tapered bolt (4) are respectively used to sleeved with flat washers (3) and rotate and install lock nuts (2); rotating the lock nut (2) at the inner side end is used to realize the axial displacement of the double-headed tapered bolt (4) outward; the double-headed tapered bolt (4) with outward axial displacement expands the expansion sleeve (6) through its tapered structure (402), and the inlay block workpiece (8) is concentrically positioned and fixedly connected through the expanded expansion sleeve (6) to form a hole; the lock nut (2) at the outer side end is used to limit and fix the outer end face of the inlay block workpiece (8) forming a hole.

4. The inlaid block expansion sleeve type positioning and locking device according to claim 1 or 2, characterized in that: On the upper end face of the base bottom plate (101) of the base (1), two vertical plates (102) are provided at intervals and in parallel; the through holes (1021) respectively made in the two vertical plates (102) at intervals and in parallel are horizontally concentrically arranged.

5. The inlaid block expansion sleeve type positioning and locking device according to claim 1 or 2, characterized in that: The through holes (1021) respectively made in the vertical plates (102) of the front and rear bases (1) are horizontally arranged at the same height.

6. The inlaid block expansion sleeve type positioning and locking device according to claim 4, wherein: The vertical plates (102) at intervals and in parallel are positioned and connected through a vertical plate support block (103); the vertical plate support block (103) is vertically fixedly connected to the inner end face of the vertical plate (102) and the upper end face of the base bottom plate (101).

7. The inlaid block expansion sleeve type positioning and locking device according to claim 6, characterized in that: The vertical plate support block (103) is of a V-shaped structure.

8. The insert block expansion sleeve type positioning and locking device according to claim 2 or 6, characterized in that: The base bottom plate (101) and the vertical plate (102) are of an integral structure.

9. The inlaid block expansion sleeve type positioning and locking device according to claim 3, wherein: The axial end face of the expansion sleeve (6) is provided with a guiding structure.

10. The inlaid block expansion sleeve type positioning and locking device according to claim 3, wherein: The tension sleeve (6) is a tension sleeve processed from spring steel containing manganese elements.

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