Adjustable tailor-welding type tool for scalloped segment of stainless steel rocket storage tank

Abstract

The utility model provides an adjustable tailor-welding type tool for a scalloped segment of a stainless steel rocket storage tank. The adjustable tailor-welding type tool comprises a scalloped segment rotating supporting assembly, a scalloped segment inner tube and a lifting shaft. The scalloped segment rotary supporting assembly is used for supporting the scalloped segment inner tube and the scalloped segment bottom; the scalloped segment inner tube is used for supporting the inner side surface of the scalloped segment; the lifting shaft is arranged in the middle of the scalloped segment rotating and supporting assembly; the lifting shaft is provided with a plurality of upper pressing mechanism supporting bases in the circumferential direction of the lifting shaft, and the upper pressing mechanism supporting bases are used for supporting the upper ends of scalloped segments. The multiple upper pressing mechanism supporting bases can rotate in the circumferential direction of the lifting shaft so as to adjust the distance between the adjacent scalloped segments. According to the adjustable tailor-welding type tool, the cutting and welding assembly precision of the scalloped segment can be improved.

Description

Technical Field

[0001] The utility model relates to the field of rocket tanks, in particular to an adjustable welding tool for melon-shaped segments of stainless steel rocket tanks. Background Art

[0002] In the existing large-diameter stainless steel rocket tank manufacturing process, there are several major difficulties in manufacturing the melon-shaped segments of the stainless steel tank. First, the secondary clamping is difficult to control: the melon segment itself is a stainless steel plate with an elliptical arc shape. The plate is thin and has low rigidity. The secondary clamping is prone to deformation, which causes the gap of the assembly weld to change, resulting in reduced welding accuracy. Second, the dimensional accuracy of the single melon segment and the dimensional accuracy of the melon segment butt welding assembly are high: the stainless steel head is large in size, and the melon segment plate is very thin, so the melon segment shape retention is high. Third, the manufacturing process is complicated. Therefore, the welding of the melon segment segment can usually only be done by online cutting and online welding.

[0003] In order to improve the welding accuracy of melon slices, it is particularly important to design an adjustable welding tool for the melon slice section of stainless steel rocket tanks. Utility Model Content

[0004] The purpose of the utility model is to overcome the deficiencies of the prior art and provide an adjustable welding tool for the melon-shaped segments of a stainless steel rocket tank.

[0005] The utility model provides an adjustable welding tooling for the melon segment of a stainless steel rocket tank, comprising: a melon segment rotating support assembly, a melon segment inner tube and a lifting shaft; the melon segment rotating support assembly is used to support the melon segment inner tube and the bottom of the melon segment; the melon segment inner tube is used to support the inner side of the melon segment; the lifting shaft is arranged in the middle of the melon segment rotating support assembly; the lifting shaft is provided with a plurality of upper clamping mechanism support bases along its circumferential direction, and the plurality of upper clamping mechanism support bases are used to support the upper end portion of the melon segment; the plurality of upper clamping mechanism support bases can all rotate around the circumferential direction of the lifting shaft to adjust the distance between adjacent melon segments.

[0006] According to one embodiment of the present invention, it also includes an upper pressing mechanism base sleeve; the upper pressing mechanism base sleeve is fixedly sleeved on the lifting shaft, and the upper pressing mechanism support base is rotatable relative to the circumferential direction of the upper pressing mechanism base sleeve.

[0007] According to one embodiment of the present invention, the upper end portion of the upper clamping mechanism base sleeve is provided with a support base positioning module corresponding to the upper clamping mechanism support base along its circumferential direction; the support base positioning module includes a support base positioning drive cylinder and a support base positioning block; along the circumferential direction of the upper clamping mechanism base sleeve, multiple support base positioning modules are fixedly connected end to end in sequence to form a circular ring; the support base positioning block is used to be fixedly connected to the upper clamping mechanism support base; the support base positioning drive cylinder is extended and retracted to control the distance between adjacent support base positioning blocks to adjust the position of the upper clamping mechanism support base in the circumferential direction.

[0008] According to one embodiment of the present invention, the upper pressing mechanism support base is provided with a melon slice upper pressing mechanism along its circumferential direction, and the melon slice upper pressing mechanism is used to press the top of the melon slice to the upper pressing mechanism support base or release the melon slice.

[0009] According to one embodiment of the present invention, the melon slice rotating support assembly is provided with a melon slice inner tube lower pressing mechanism along its circumferential direction, and the melon slice inner tube lower pressing mechanism is used to press the bottom of the melon slice tightly against the melon slice inner tube or release the melon slice.

[0010] According to one embodiment of the present invention, a support base is further included; the melon slice rotation support assembly is rotatably disposed on the support base to drive the melon slice inner tube and the melon slice to rotate.

[0011] According to one embodiment of the present invention, a melon segment outer pressing component is further included; the melon segment outer pressing component is used to press the melon segment to the melon segment inner tube from the outer side of the melon segment or release the melon segment.

[0012] According to one embodiment of the present utility model, the lifting shaft is also provided with an upper clamping mechanism base limiting sleeve; the upper clamping mechanism base limiting sleeve is fixedly sleeved on the lower end portion of the upper clamping mechanism base shaft sleeve, the diameter of the upper clamping mechanism base limiting sleeve is larger than the diameter of the upper clamping mechanism base shaft sleeve, and the upper clamping mechanism base limiting sleeve is used to support the lower end portion of the upper clamping mechanism support base.

[0013] According to one embodiment of the present invention, the melon slice upper pressing mechanism includes an upper pressing drive cylinder and an upper pressing block, and the upper pressing drive cylinder drives the upper pressing block toward or away from the top of the melon slice by telescoping.

[0014] According to one embodiment of the present invention, the melon slice inner tube lower pressing mechanism includes a lower pressing drive cylinder and a lower pressing block, and the lower pressing drive cylinder drives the lower pressing block toward or away from the melon slice by telescoping.

[0015] According to the utility model of the adjustable welding tooling for the melon-peel section of a stainless steel rocket tank, the distance between adjacent melon-peel segments can be adjusted, and the cutting or welding position of the longitudinal seam of the melon-peel segment can be adjusted by rotating the upper clamping mechanism support base in the circumferential direction around the lifting axis.

[0016] It should be understood that the above general description and the following detailed description are merely exemplary and illustrative and are not intended to limit the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The following drawings are part of the specification of the present utility model, which illustrate exemplary embodiments of the present utility model. The accompanying drawings and the description of the specification are used to explain the principle of the utility model.

[0018] Figure 1 This is a perspective view of an adjustable tailor-welded tooling for a stainless steel rocket tank melon segment according to one embodiment of the present invention;

[0019] Figure 2 This is a perspective view of an adjustable tailor-welded tooling for a stainless steel rocket tank melon segment according to one embodiment of the present utility model;

[0020] Figure 3 This is a three-dimensional diagram of a support base of an upper pressing mechanism according to an embodiment of the present invention;

[0021] Figure 4 This is a cross-sectional view of the upper pressing mechanism support base according to one embodiment of the present invention;

[0022] Figure 5 This is a three-dimensional diagram of a support base positioning module according to an embodiment of the present invention;

[0023] Figure 6 This is a perspective view of an adjustable tailor-welded tooling for a stainless steel rocket tank melon segment according to one embodiment of the present invention;

[0024] Figure 7 This is a three-dimensional diagram of a limiting collar of the upper pressing mechanism base according to an embodiment of the present invention;

[0025] Figure 8 This is a three-dimensional diagram of a melon slice upper pressing mechanism according to an embodiment of the present invention;

[0026] Figure 9 It is a three-dimensional diagram of a lower pressing drive cylinder according to an embodiment of the present utility model.

[0027] Description of reference numerals:

[0028] 1-1 Melon slice inner tube; 1-2 Melon slice upper pressing mechanism; 1-3 Melon slice inner tube lower pressing mechanism; 1-4 Inner tube mold base; 1-5 Melon slice rotating support assembly; 1-6 Support base; 1-16 Lifting shaft;

[0029] 1-2-2 Upper clamping drive cylinder; 1-2-3 Upper clamping block; 1-3-1 Lower clamping drive cylinder; 1-3-2 Lower clamping block; 1-14-1 Upper clamping mechanism base sleeve; 1-14-2 Upper clamping mechanism base limiting ring; 1-14-3 Upper clamping mechanism support base; 1-14-4 Support base positioning module; 1-14-4-1 Support base positioning drive cylinder; 1-14-4-2 Support base positioning block; 2- Melon slice outer clamping component. DETAILED DESCRIPTION

[0030] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are used to illustrate the principles of the present invention, and are not configured to limit the present invention. In addition, the structural components in the drawings are not necessarily drawn to scale. For example, the dimensions of some structural components or areas in the drawings may be enlarged for other structural components or areas to facilitate understanding of the embodiments of the present invention.

[0031] The directional words that appear in the following description refer to the directions shown in the drawings and do not limit the specific structure of the embodiments of the present invention. In the description of the present invention, it should be noted that, unless otherwise specified, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can be directly connected or indirectly connected through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0032] In addition, the terms "include", "comprising", "having" or any other variations thereof are intended to cover non-exclusive inclusion, so that a structure or component comprising a series of elements includes not only those elements, but also other mechanical elements not explicitly listed or inherent in the structure or component. In the absence of more limitations, the elements defined by the sentence "comprising..." do not exclude the presence of other identical elements in the article or device comprising the elements.

[0033] Spatially relative terms such as "below," "beneath," "under," "low," "above," "on," "high," and the like are used to facilitate description to explain the positioning of one element relative to a second element, indicating that these terms are intended to encompass different orientations of the device in addition to those shown in the figures. Additionally, for example, "one element is above / below another element" may indicate that the two elements are in direct contact, or may indicate that there are other elements between the two elements. Furthermore, terms such as "first," "second," and the like are also used to describe various elements, regions, portions, and the like, and do not specifically refer to an order or sequence, and should not be considered limiting. Similar terms are used throughout the description to indicate similar elements.

[0034] In the following description of the present invention, in certain scenarios, only the terms "rocket", "carrier rocket", "spacecraft", "space carrier" or "missile" may be used. This is only for the convenience of description, and its connotation is not limited to the specific words used. Generally speaking, the rockets of the present invention include carrier rockets or space carriers used to carry satellites, spacecraft or other probes, as well as various types of missiles, rockets and other weapons used to carry military payloads, as well as similar products that can send payloads into the air. When interpreting the above-mentioned specific terms, those skilled in the art shall not limit the rocket to only one of the carrier rockets or missiles based on the specific words used to describe the scenario, thereby narrowing the scope of protection of the present invention.

[0035] For those skilled in the art, the present invention can be implemented without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present invention by illustrating examples of the present invention.

[0036] Figure 1 This is a perspective view of an adjustable tailor-welded tooling for a stainless steel rocket tank melon segment according to one embodiment of the present invention; Figure 2 This is a perspective view of an adjustable tailor-welded tooling for a stainless steel rocket tank melon segment according to one embodiment of the present utility model; Figure 3 This is a three-dimensional diagram of a support base of an upper pressing mechanism according to an embodiment of the present invention; Figure 4 This is a cross-sectional view of the upper pressing mechanism support base according to one embodiment of the present invention; Figure 5 This is a three-dimensional diagram of a support base positioning module according to an embodiment of the present invention; Figure 6 This is a perspective view of an adjustable tailor-welded tooling for a stainless steel rocket tank melon segment according to one embodiment of the present invention; Figure 7 This is a three-dimensional diagram of a limiting collar of the upper pressing mechanism base according to an embodiment of the present invention; Figure 8 This is a three-dimensional diagram of a melon slice upper pressing mechanism according to an embodiment of the present invention; Figure 9It is a three-dimensional diagram of a lower pressing drive cylinder according to an embodiment of the present utility model.

[0037] like Figure 1 、 2 As shown in Figure 3, the utility model provides an adjustable welding tooling for the melon segment of a stainless steel rocket tank, comprising: a melon segment rotating support assembly 1-5, a melon segment inner tube 1-1 and a lifting shaft 1-16. The melon segment rotating support assembly 1-5 is used to support the melon segment inner tube 1-1 and the bottom of the melon segment, and the melon segment inner tube 1-1 is used to support the inner side of the melon segment. The lifting shaft 1-16 is arranged in the middle of the melon segment rotating support assembly 1-5. The lifting shaft 1-16 is provided with a plurality of upper clamping mechanism support bases 1-14-3 along its circumferential direction, and the plurality of upper clamping mechanism support bases 1-14-3 are used to support the upper end of the melon segment. The plurality of upper clamping mechanism support bases 1-14-3 can all rotate around the circumferential direction of the lifting shaft 1-16 to adjust the distance between adjacent melon segments.

[0038] In this embodiment, the upper clamping mechanism support base 1-6 can be placed one-to-one corresponding to the melon slices. By rotating the upper clamping mechanism support base 1-14-3 in the circumferential direction around the lifting shaft 1-16, the distance between adjacent melon slices can be adjusted, and the cutting or welding position of the longitudinal seam of the melon slices can be adjusted to control the size and accuracy of the welded melon slice segments.

[0039] like Figure 4 As shown, according to one embodiment of the present invention, in addition to the melon slice rotation support assembly 1-5, the melon slice inner tube 1-1, and the lifting shaft 1-16, the adjustable tailor-welded tooling also includes an upper clamping mechanism base sleeve 1-14-1. The upper clamping mechanism base sleeve 1-14-1 is fixedly mounted on the lifting shaft 1-16, and the upper clamping mechanism support base 1-14-3 is rotatable relative to the circumferential direction of the upper clamping mechanism base sleeve 1-14-1.

[0040] In this embodiment, the upper clamping mechanism support base 1-14-3 can be rotatably arranged relative to the circumferential direction of the upper clamping mechanism base sleeve 1-14-1 to adjust the position of the upper end of the melon slices, thereby ensuring the welding accuracy of the upper ends of adjacent melon slices.

[0041] like Figure 5 As shown, according to one embodiment of the present invention, a support base positioning module 1-14-4 corresponding to the upper clamping mechanism support base 1-14-3 is provided along the circumferential direction of the upper end portion of the upper clamping mechanism base sleeve 1-14-1. The support base positioning module 1-14-4 includes a support base positioning drive cylinder 1-14-4-1 and a support base positioning block 1-14-4-2. Figure 3As shown, along the circumferential direction of the upper clamping mechanism base sleeve 1-14-1, multiple support base positioning modules 1-14-4 are fixedly connected end to end to form a ring. The support base positioning blocks 1-14-4-2 are used to be fixedly connected to the upper clamping mechanism support base 1-14-3. The support base positioning drive cylinder 1-14-4-1 is extended and retracted to control the distance between adjacent support base positioning blocks 1-14-4-2 to adjust the circumferential position of the upper clamping mechanism support base 1-14-3.

[0042] The adjustable welding tooling of this embodiment can adjust the position of the corresponding melon slice in the circumferential direction by extending and retracting the support base positioning drive cylinder 1-14-4-1, thereby improving the accuracy of melon slice welding.

[0043] According to one embodiment of the present invention, the upper pressing mechanism support base 1-14-3 is provided with a melon slice upper pressing mechanism 1-2 along its circumferential direction, and the melon slice upper pressing mechanism 1-2 is used to press the top of the melon slice to the upper pressing mechanism support base 1-14-3 or release the melon slice.

[0044] The adjustable welding tooling of this embodiment can control the welding accuracy of the longitudinal seam of the melon slices by pressing the top or upper end of the melon slices to the upper pressing mechanism support base 1-14-3 through the upper pressing mechanism 1-2 of the melon slices.

[0045] According to one embodiment of the present invention, the melon slice rotating support assembly 1-5 is provided with a melon slice inner tube lower pressing mechanism 1-3 along its circumferential direction, and the melon slice inner tube lower pressing mechanism 1-3 is used to press the bottom of the melon slice tightly against the melon slice inner tube 1-1 or release the melon slice.

[0046] In this embodiment, the melon segment rotation support assembly can be provided with multiple melon segment inner tube lower clamping mechanisms 1-3 along its circumferential direction. For example, three melon segment inner tube lower clamping mechanisms 1-3 can be provided for each melon segment to better fit the lower portion of the melon segment to the melon segment inner tube, ensuring assembly accuracy during cutting and welding. This adjustable tailor-welding tooling, through the melon segment inner tube lower clamping mechanisms, allows the melon segment (particularly the lower portion) to fit to the melon segment inner tube, improving the cutting and welding assembly accuracy of the melon segment.

[0047] According to one embodiment of the present invention, in addition to the melon slice rotation support assembly 1-5, the melon slice inner tube 1-1, and the lifting shaft 1-16, the adjustable tailor-welded tooling also includes a support base 1-6. The melon slice rotation support assembly 1-5 is rotatably mounted on the support base 1-6 to drive the melon slice inner tube 1-1 and the melon slices to rotate.

[0048] The adjustable welding tooling of this embodiment, by providing a melon slice rotating support assembly that can rotate around a support base, can achieve welding of all melon slice longitudinal seams without moving the positions of the welding equipment and the cutting equipment, thereby ensuring the consistency of the weld quality.

[0049] like Figure 6 As shown, according to one embodiment of the present invention, in addition to the melon segment rotation support assembly 1-5, the melon segment inner tube 1-1, and the lifting shaft 1-16, the adjustable tailor-welded tooling also includes a melon segment outer pressing component 2. The melon segment outer pressing component 2 is used to press the melon segment against the melon segment inner tube 1-1 from the outer side of the melon segment or release the melon segment.

[0050] In this embodiment, the melon segment outer pressing component 2 can make the melon segment fit to the melon segment inner tube, which can ensure the cutting and welding assembly accuracy of the melon segment and keep the melon segment or melon segment in shape.

[0051] like Figure 7 As shown, according to one embodiment of the present invention, the lifting shaft 1-16 is further provided with an upper clamping mechanism base limiting collar 1-14-2. The upper clamping mechanism base limiting collar 1-14-2 is fixedly sleeved on the lower end of the upper clamping mechanism base shaft sleeve 1-14-1. The diameter of the upper clamping mechanism base limiting collar 1-14-2 is larger than the diameter of the upper clamping mechanism base shaft sleeve 1-14-1. The upper clamping mechanism base limiting collar 1-14-2 is used to support the lower end of the upper clamping mechanism support base 1-14-3.

[0052] In this embodiment, the lower end portion of the upper clamping mechanism support base 1-14-3 can rotate circumferentially relative to the upper clamping mechanism base limiting ring 1-14-2.

[0053] like Figure 8 As shown, according to one embodiment of the present invention, the melon slice upper pressing mechanism 1-2 includes an upper pressing drive cylinder 1-2-2 and an upper pressing block 1-2-3. The upper pressing drive cylinder 1-2-2 drives the upper pressing block 1-2-3 toward or away from the top of the melon slice by telescoping.

[0054] The welding equipment of this embodiment can press the melon slices (especially the upper part of the melon slices) to the upper pressing mechanism base through the melon slice upper pressing mechanism, thereby improving the cutting and welding assembly accuracy of the melon slices. The upper pressing block is used to press the end face of the melon slice, and can be an arc-shaped surface that matches the outer side surface of the melon slice. A plurality of melon slice upper pressing mechanisms 1-2 can be set along the circumferential direction of the upper pressing mechanism support base 1-14-3. For example, two melon slice upper pressing mechanisms 1-2 can be set for each melon slice, so that the upper part of the melon slice can be better fitted to the upper pressing mechanism support base 1-14-3, thereby ensuring the assembly accuracy of cutting and welding.

[0055] like Figure 9 As shown, according to one embodiment of the present invention, the melon slice inner tube lower clamping mechanism 1-3 includes a lower clamping drive cylinder 1-3-1 and a lower clamping block 1-3-2, and the lower clamping drive cylinder 1-3-1 drives the lower clamping block 1-3-2 toward or away from the melon slice by telescoping.

[0056] In this embodiment, the lower pressing block is used to press the end surface of the melon slice, and can be an arc-shaped surface that matches the outer surface of the melon slice.

[0057] The utility model provides an adjustable welding tool for the melon-shaped segment of a stainless steel rocket tank, and the related drive cylinder equipment (such as the upper clamping drive cylinder 1-2-2, the lower clamping drive cylinder 1-3-1, etc.) can be a pneumatic cylinder, an electric cylinder, etc.

[0058] The above embodiments of the present invention can be combined with each other and have corresponding technical effects.

[0059] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An adjustable welding tool for the melon-shaped segments of a stainless steel rocket tank, characterized in that: include: Melon segment rotation support assembly, melon segment inner tube and lifting shaft; The melon segment rotating support assembly is used to support the melon segment inner tube and the bottom of the melon segment; the melon segment inner tube is used to support the inner side of the melon segment; the lifting shaft is set in the middle of the melon segment rotating support assembly; The lifting shaft is provided with a plurality of upper pressing mechanism support bases along its circumferential direction, and the plurality of upper pressing mechanism support bases are used to support the upper end portions of the melon slices; the plurality of upper pressing mechanism support bases can all rotate around the circumferential direction of the lifting shaft to adjust the distance between adjacent melon slices.

2. The adjustable tailor-welded tooling according to claim 1, characterized in that: It also includes an upper pressing mechanism base sleeve; the upper pressing mechanism base sleeve is fixedly sleeved on the lifting shaft, and the upper pressing mechanism support base is rotatable relative to the circumferential direction of the upper pressing mechanism base sleeve.

3. The adjustable tailor-welded tooling according to claim 2, characterized in that: The upper end portion of the upper clamping mechanism base sleeve is provided with a support base positioning module corresponding to the upper clamping mechanism support base along its circumferential direction; the support base positioning module includes a support base positioning drive cylinder and a support base positioning block; along the circumferential direction of the upper clamping mechanism base sleeve, multiple support base positioning modules are fixedly connected end to end in sequence to form a circular ring; the support base positioning block is used to be fixedly connected to the upper clamping mechanism support base; the support base positioning drive cylinder is extended and retracted to control the distance between adjacent support base positioning blocks to adjust the position of the upper clamping mechanism support base in the circumferential direction.

4. The adjustable tailor-welded tooling according to claim 1, characterized in that: The upper pressing mechanism support base is provided with a melon slice upper pressing mechanism along its circumferential direction, and the melon slice upper pressing mechanism is used to press the top of the melon slice to the upper pressing mechanism support base or release the melon slice.

5. The adjustable tailor-welded tooling according to claim 1, characterized in that: The melon slice rotating support assembly is provided with a melon slice inner tube lower pressing mechanism along its circumferential direction, and the melon slice inner tube lower pressing mechanism is used to press the bottom of the melon slice tightly against the melon slice inner tube or release the melon slice.

6. The adjustable tailor-welded tooling according to claim 1, characterized in that: It also includes a support base; the melon slice rotation support assembly is rotatably arranged on the support base to drive the melon slice inner tube and the melon slice to rotate.

7. The adjustable tailor-welded tooling according to claim 1, characterized in that: It also includes a melon segment outer pressing component; the melon segment outer pressing component is used to press the melon segment to the melon segment inner tube from the outer side of the melon segment or release the melon segment.

8. The adjustable tailor-welded fixture according to claim 2, characterized in that: The lifting shaft is also provided with an upper clamping mechanism base limiting sleeve; the upper clamping mechanism base limiting sleeve is fixedly sleeved on the lower end portion of the upper clamping mechanism base shaft sleeve, the diameter of the upper clamping mechanism base limiting sleeve is larger than the diameter of the upper clamping mechanism base shaft sleeve, and the upper clamping mechanism base limiting sleeve is used to support the lower end portion of the upper clamping mechanism support base.

9. The adjustable tailor-welded tooling according to claim 4, characterized in that: The melon slice upper pressing mechanism includes an upper pressing drive cylinder and an upper pressing block. The upper pressing drive cylinder drives the upper pressing block toward or away from the top of the melon slice by telescoping.

10. The adjustable tailor-welded tooling according to claim 5, characterized in that: The melon slice inner tube lower pressing mechanism includes a lower pressing drive cylinder and a lower pressing block. The lower pressing drive cylinder drives the lower pressing block toward or away from the melon slice by telescoping.

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