阅读说明：本技术 一种城际车主吊梁的组焊工艺及城际车主吊梁 (Assembly welding process for intercity vehicle main hanging beam and intercity vehicle main hanging beam ) 是由 许洪华 刘双剑 汪利军 于 2020-12-29 设计创作，主要内容包括：本发明适用于制造技术领域,提供了一种城际车主吊梁的组焊工艺及城际车主吊梁,该组焊工艺包括以下步骤：将待组焊的纵梁两端保留焊后机加工余量,并标记出型材中心线；以型材中心线位基准进行焊前机加工及组装点焊；在完成横梁与纵梁及筋板的组装点焊后,测量对角线,通过对角线的大小确定横梁与纵梁间焊缝的施焊顺序及方向；确认施焊方向后,将主吊梁的主体部分焊接放在变位工装上,进行横梁对接焊缝焊接和横梁角接焊缝焊接,并在主吊梁横梁与纵梁之间角焊缝增加焊接垫板。本发明提供的组焊工艺可调整主吊梁的内轮廓,减少主吊梁的调校工作量,减少人为翻边工作量,使焊接位置更容易达到,焊缝质量得到保证。(The invention is suitable for the technical field of manufacturing, and provides an assembly welding process of an intercity vehicle owner hanging beam and the intercity vehicle owner hanging beam, wherein the assembly welding process comprises the following steps: reserving machining allowance after welding at two ends of the longitudinal beam to be welded, and marking a central line of the section; performing machining before welding and assembling spot welding by using the center line position reference of the section; after the assembly spot welding of the cross beam, the longitudinal beam and the rib plate is completed, measuring a diagonal line, and determining the welding sequence and the welding direction of a welding line between the cross beam and the longitudinal beam according to the size of the diagonal line; after the welding direction is confirmed, the main body part of the main hanging beam is welded on a displacement tool, cross beam butt weld joint welding and cross beam fillet weld joint welding are carried out, and a welding backing plate is additionally arranged on the fillet weld joint between the cross beam and the longitudinal beam of the main hanging beam. The assembly welding process provided by the invention can adjust the inner contour of the main hanging beam, reduce the adjustment workload of the main hanging beam, reduce the workload of artificial flanging, enable the welding position to be more easily reached and ensure the quality of a welding seam.)

1. An assembly welding process of an intercity vehicle main hanging beam is characterized by comprising the following steps:

reserving machining allowance after welding at two ends of the longitudinal beam to be welded, and marking a central line of the section;

performing machining before welding and assembling spot welding by using the center line position reference of the section;

after the assembly spot welding of the cross beam, the longitudinal beam and the rib plate is completed, measuring a diagonal line, and determining the welding sequence and the welding direction of a welding line between the cross beam and the longitudinal beam according to the size of the diagonal line;

after the welding direction is confirmed, the main body part of the main hanging beam is welded on a displacement tool, cross beam butt weld joint welding and cross beam fillet weld joint welding are carried out, and a welding backing plate is additionally arranged on the fillet weld joint between the cross beam and the longitudinal beam of the main hanging beam.

2. The assembly welding process of the intercity vehicle main hanging beam as claimed in claim 1, wherein machining allowance after welding is 80-120 mm.

3. The assembly welding process of the intercity truck main hanging beam according to claim 1, characterized in that in the step, in the process of assembly welding of the longitudinal beams and the cross beams, the distance between the two longitudinal beams is 5-7 mm, and the distance between the two ends of each longitudinal beam is 2-4 mm.

4. The assembly welding process of the intercity main hanging beam according to claim 1, wherein in the step, in the assembly spot welding process, the two cross beams are respectively placed by 0.5-1.5 mm towards two sides by taking the center line of the longitudinal beam as a reference, and the assembling height of the rib plate is 2-4 mm higher than the machining plane of the main hanging beam.

5. The assembly welding process of the intercity truck main hanging beam as claimed in claim 1, wherein the step of determining the welding sequence and direction of the welding seam between the cross beam and the longitudinal beam through the size of the diagonal line specifically comprises:

welding two opposite angles with large diagonal lines in opposite directions, and welding two opposite angles with small diagonal lines in opposite directions.

6. The assembly welding process of an intercity main hanging beam as claimed in claim 1, wherein in the step, the deflection tool is designed to be provided with one main hanging beam at each side, the main hanging beams are symmetrically assembled on the deflection tool in a non-machining surface outward mode, the threaded pull rod of the deflection tool is used for making the longitudinal beams at the two ends into welding reverse deformation with the middle protruding outwards, and the mode of symmetrically welding the two main hanging beams is adopted in the welding process of the main hanging beams.

7. An inter-city vehicle main hanging beam processed by the assembly welding process according to any one of claims 1-6.

Technical Field

The invention belongs to the technical field of manufacturing, and particularly relates to an assembling and welding process of an intercity vehicle owner hanging beam and the intercity vehicle owner hanging beam.

Background

The speed of the motor train unit along with the train is continuously improved, the requirement on the performance of a traction transformer of the motor train unit is higher and higher, the main hanging beam is used as an installation facility of the traction transformer, the main hanging beam is not only subjected to static load due to the weight of the traction transformer and a cooling oil tank, but also can be subjected to dynamic load along with the change of the speed and the vibration in the running process of the motor train, and the requirement on safety is higher and higher.

Therefore, the welding seam quality of the intercity main hanging beam is extremely important, the welding seam of the intercity main hanging beam requires the welding seam of CPC2, the inspection grade is CT3, the welding seam defect grade is C, the standard requires 100% of nondestructive detection, in addition, the welding seam fusion depth of the boundary beam is large, the multilayer multi-pass welding easily generates defects such as insufficient fusion depth, non-fusion between layers and the like; the requirements on flatness, straightness, verticality and diagonal difference are high, the adjustment difficulty is high, and the market demand can not be well met; the welding position of the welding seam is difficult to reach, and the welding quality can not be well ensured.

Disclosure of Invention

The embodiment of the invention aims to provide an assembly welding process of an intercity vehicle main hanging beam, and aims to solve the problems in the background technology.

The embodiment of the invention is realized in such a way that the assembly welding process of the intercity main hoisting beam comprises the following steps:

reserving machining allowance after welding at two ends of the longitudinal beam to be welded, and marking a central line of the section;

performing machining before welding and assembling spot welding by using the center line position reference of the section;

after the assembly spot welding of the cross beam, the longitudinal beam and the rib plate is completed, measuring a diagonal line, and determining the welding sequence and the welding direction of a welding line between the cross beam and the longitudinal beam according to the size of the diagonal line;

after the welding direction is confirmed, the main body part of the main hanging beam is welded on a displacement tool, cross beam butt weld joint welding and cross beam fillet weld joint welding are carried out, and a welding backing plate is additionally arranged on the fillet weld joint between the cross beam and the longitudinal beam of the main hanging beam.

As another preferable scheme of the embodiment of the invention, the machining allowance after welding is 80-120 mm.

In another preferable scheme of the embodiment of the invention, in the step, in the process of assembling and welding the longitudinal beams and the cross beams, the placing amount between the two longitudinal beams is 5-7 mm, and the placing amount at each of two ends is 2-4 mm.

In another preferable scheme of the embodiment of the invention, in the step, in the assembling and spot welding process, the two cross beams are respectively placed by 0.5-1.5 mm towards two sides by taking the center line of the longitudinal beam as a reference, and the assembling height of the rib plate is 2-4 mm higher than the machining plane of the main hanging beam.

As another preferable scheme of the embodiment of the present invention, the step of determining the welding sequence and direction of the weld between the cross beam and the longitudinal beam according to the size of the diagonal line specifically includes:

welding two opposite angles with large diagonal lines in opposite directions, and welding two opposite angles with small diagonal lines in opposite directions.

As another preferable scheme of the embodiment of the present invention, in the step, the displacement tool is designed such that two sides of the displacement tool are respectively provided with one main suspension beam, the main suspension beams are symmetrically assembled to the displacement tool in a manner that the non-machined surface faces outwards, the displacement tool threaded pull rod is used to make the longitudinal beams at the two ends into welding reversible deformation with convex middle parts, and a manner of symmetrically welding the two main suspension beams is adopted in the welding process of the main suspension beams.

Another object of the embodiments of the present invention is to provide an inter-city vehicle main hanging beam processed by the above assembly welding process.

According to the assembling and welding process of the intercity truck main hanging beam provided by the embodiment of the invention, the machining allowance after welding is reserved in advance, so that the overall dimensional tolerance and the action tolerance are smaller; welding discharge and welding reversible deformation are adjusted, and post-welding adjustment workload is reduced; through the adjustment of welding sequence and welding direction, the interior profile of adjustment main hanging beam reduces the timing work load of main hanging beam, puts the welding process of main hanging beam on the machine of shifting, reduces artificial turn-ups work load, makes the welding position reach more easily, and the welding seam quality obtains guaranteeing.

Drawings

FIG. 1 is a schematic view of a single stringer machining.

FIG. 2 is a schematic view of a fillet weld joint.

Fig. 3 is a schematic view of a structure of a bonding pad.

In fig. 1, a indicates a machining allowance after welding, and Z indicates a profile center line.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The embodiment provides an assembling and welding process of an intercity vehicle main hanging beam, which comprises the following steps:

and S1, as shown in the attached figure 1, reserving 100mm of post-welding machining allowance at two ends of each of the two longitudinal beams, drawing a central line of the section on the section by laser, performing pre-welding machining and assembly spot welding by using the central line position reference of the section, and machining to a qualified size in the post-welding integral machining process. The thickness of the four-corner rib plate is changed from 10mm to 16mm, the thickness of the cross beam patch plate is changed from 6mm to 10mm, the assembling height of the rib plate is 3mm higher than a machining plane in the assembling process, the patch plate is 2mm higher than the machining plane, the excess is increased in the whole machining process after welding, the flatness of the main hanging beam caused by collapse under welding is prevented from being out of tolerance, and the thickness of the rib plate and the patch plate after machining is ensured to meet the drawing requirements. In addition, the distance between the two longitudinal beams is 6mm, the distance between the two ends of the longitudinal beams is 3mm, the consistency of the gaps of the welding seams at the two ends is ensured, the distance between the two transverse beams is 1mm towards the two sides by taking the central line of the longitudinal beams as a reference, the assembling height of the rib plate is 3mm higher than the machining plane of the main hanging beam, and the thickness of the machined rib plate is ensured to meet the drawing requirements.

S2, after the assembly platform completes assembly spot welding of the cross beam, the longitudinal beam and the rib plate, measuring diagonal lines, determining welding sequence and direction of welding lines between the cross beam and the longitudinal beam according to the size of the diagonal lines, welding two diagonal lines with large diagonal lines in a first welding mode and welding the two diagonal lines with small diagonal lines in a reverse welding mode, welding the two diagonal lines with small diagonal lines in opposite directions, marking the welding sequence and the welding direction on the main hanging beam by using a marking pen, welding the main hanging beam on a position-changing tool according to the marking sequence and the marking direction, and adjusting the integral inner contour of the main hanging beam through welding.

And S3, after the welding direction is confirmed, the main body part of the main hanging beam is welded on a displacement tool, the welding seam with the original welding position being PF is displaced to be a PB position, manual flanging of the main hanging beam is reduced, workload is reduced, and beam butt welding seam welding and beam fillet welding seam welding are carried out. The main hanging beam is symmetrically assembled on the displacement tool in a mode that a non-machining surface faces outwards, deformation of the displacement tool caused by welding deformation of the main hanging beam on one side is prevented, deformation exceeding scrapping caused by deformation of the displacement tool due to multiple accumulated deformation is avoided, the service life of the displacement tool is prolonged, the longitudinal beams on two ends are made into middle convex welding reversible deformation by using the displacement tool threaded pull rod, two main hanging beams are symmetrically welded in the welding process of the main hanging beams, and the influence of deformation of the main hanging beams on the displacement tool is reduced as much as possible on the premise of ensuring that deformation of the main hanging beams is reduced. In addition, a welding backing plate is additionally arranged on a fillet weld between the main hanging beam cross beam and the longitudinal beam, so that the weld penetration is ensured, the back side is prevented from being welded to form sagging, and the weld quality is greatly improved. The schematic diagram of the fillet weld between the cross beam and the longitudinal beam of the main hanging beam is shown in the attached drawing 2, and the structural schematic diagram of the welding backing plate is shown in the attached drawing 3.

Specifically, in practical application, the assembly welding process applied to the preparation of the intercity truck main hanging beam may include the following steps:

the first step is as follows: preparing before welding, and checking whether the field temperature and humidity, the protective gas, the welding wire and the welding machine have good performance. Performing a pre-welding process test under the condition that the field temperature and humidity meet the requirements, welding a welding seam with the length of more than 200mm by using an 8mm aluminum plate, and then performing welding process test detection by a welding supervisor; the second step is that: cleaning and polishing, cleaning oil stain 50mm away from a part to be welded with a welding seam with a cleaning agent, and then polishing an oxide film 30mm away from the part to be welded with the welding seam with a mechanical polishing machine; the third step: assembling and spot-welding, namely assembling according to the requirements of a drawing, wherein the distance between two longitudinal beams is 6mm, the distance between two ends of each longitudinal beam is 3mm, the consistency of the gaps of welding seams at two ends is ensured, the distance between two cross beams is 1mm towards two sides by taking the central line of the longitudinal beams as a reference, and the assembling height of the rib plate is 3mm higher than the machining plane of the main hanging beam; the fourth step: measuring a diagonal line, and then judging the welding direction according to the size of the diagonal line, wherein the opposite sides with the large diagonal line are welded oppositely, and the opposite sides with the small diagonal line are welded oppositely; after the welding direction is confirmed, the two main hanging beams are symmetrically installed on a deflection tool, and the tool thread pull rod is used for pulling the longitudinal beams at the two ends into welding reversible deformation with the middle protruding outwards, wherein the reversible deformation amount is 8 mm; the fifth step: welding the cross beam butt weld; and a sixth step: the tooling is shifted, and the angle of the beam is welded with a weld joint; the seventh step: assembling other accessories after the lower positioner is assembled, and completing welding; eighth step: self-checking, and adjusting the out-of-tolerance size and action tolerance; the ninth step: integrally machining the main hanging beam; the tenth step: and (5) fine grinding and special detection of the welding line.

Example 2

The embodiment provides an assembling and welding process of an intercity vehicle main hanging beam, which comprises the following steps:

s1, reserving 80mm of post-welding machining allowance at two ends of the two longitudinal beams respectively, drawing a profile center line on the profile by laser, performing pre-welding machining and assembly spot welding by using the profile center line position reference, and machining to a qualified size in the post-welding integral machining process. The thickness of the four-corner rib plate is changed from 10mm to 16mm, the thickness of the cross beam patch plate is changed from 6mm to 10mm, the assembling height of the rib plate is 3mm higher than a machining plane in the assembling process, the patch plate is 2mm higher than the machining plane, the excess is increased in the whole machining process after welding, the flatness of the main hanging beam caused by collapse under welding is prevented from being out of tolerance, and the thickness of the rib plate and the patch plate after machining is ensured to meet the drawing requirements. In addition, the distance between the two longitudinal beams is 5mm, the distance between the two ends of the longitudinal beams is 2mm, the consistency of the gaps of the welding seams at the two ends is ensured, the distance between the two transverse beams is 0.5mm towards the two sides by taking the central line of the longitudinal beam as a reference, the assembling height of the rib plate is 2mm higher than the machining plane of the main hanging beam, and the thickness of the rib plate after machining meets the requirements of a drawing.

S2, after the assembly platform completes assembly spot welding of the cross beam, the longitudinal beam and the rib plate, measuring diagonal lines, determining welding sequence and direction of welding lines between the cross beam and the longitudinal beam according to the size of the diagonal lines, welding two diagonal lines with large diagonal lines in a first welding mode and welding the two diagonal lines with small diagonal lines in a reverse welding mode, welding the two diagonal lines with small diagonal lines in opposite directions, marking the welding sequence and the welding direction on the main hanging beam by using a marking pen, welding the main hanging beam on a position-changing tool according to the marking sequence and the marking direction, and adjusting the integral inner contour of the main hanging beam through welding.

And S3, after the welding direction is confirmed, the main body part of the main hanging beam is welded on a displacement tool, the welding seam with the original welding position being PF is displaced to be a PB position, manual flanging of the main hanging beam is reduced, workload is reduced, and beam butt welding seam welding and beam fillet welding seam welding are carried out. The main hanging beam is symmetrically assembled on the displacement tool in a mode that a non-machining surface faces outwards, deformation of the displacement tool caused by welding deformation of the main hanging beam on one side is prevented, deformation exceeding scrapping caused by deformation of the displacement tool due to multiple accumulated deformation is avoided, the service life of the displacement tool is prolonged, the longitudinal beams on two ends are made into middle convex welding reversible deformation by using the displacement tool threaded pull rod, two main hanging beams are symmetrically welded in the welding process of the main hanging beams, and the influence of deformation of the main hanging beams on the displacement tool is reduced as much as possible on the premise of ensuring that deformation of the main hanging beams is reduced. In addition, a welding backing plate is additionally arranged on a fillet weld between the main hanging beam cross beam and the longitudinal beam, so that the weld penetration is ensured, the back side is prevented from being welded to form sagging, and the weld quality is greatly improved. The schematic diagram of the fillet weld between the cross beam and the longitudinal beam of the main hanging beam is shown in the attached drawing 2, and the structural schematic diagram of the welding backing plate is shown in the attached drawing 3.

Example 3

The embodiment provides an assembling and welding process of an intercity vehicle main hanging beam, which comprises the following steps:

and S1, reserving 120mm of post-welding machining allowance at two ends of the two longitudinal beams respectively, drawing a central line of the section on the section by laser, performing pre-welding machining and assembly spot welding by using the position reference of the central line of the section, and machining to a qualified size in the post-welding integral machining process. The thickness of the four-corner rib plate is changed from 10mm to 16mm, the thickness of the cross beam patch plate is changed from 6mm to 10mm, the assembling height of the rib plate is 3mm higher than a machining plane in the assembling process, the patch plate is 2mm higher than the machining plane, the excess is increased in the whole machining process after welding, the flatness of the main hanging beam caused by collapse under welding is prevented from being out of tolerance, and the thickness of the rib plate and the patch plate after machining is ensured to meet the drawing requirements. In addition, the placing amount between the two longitudinal beams is 7mm, the placing amount at two ends is 4mm respectively, the consistency of the gaps of welding seams at two ends is ensured, the placing amount of the two transverse beams is 1.5mm towards two sides respectively by taking the central line of the longitudinal beams as a reference, the assembling height of the rib plate is 4mm higher than the machining plane of the main hanging beam, and the thickness of the machined rib plate is ensured to meet the drawing requirements.

S2, after the assembly platform completes assembly spot welding of the cross beam, the longitudinal beam and the rib plate, measuring diagonal lines, determining welding sequence and direction of welding lines between the cross beam and the longitudinal beam according to the size of the diagonal lines, welding two diagonal lines with large diagonal lines in a first welding mode and welding the two diagonal lines with small diagonal lines in a reverse welding mode, welding the two diagonal lines with small diagonal lines in opposite directions, marking the welding sequence and the welding direction on the main hanging beam by using a marking pen, welding the main hanging beam on a position-changing tool according to the marking sequence and the marking direction, and adjusting the integral inner contour of the main hanging beam through welding.

And S3, after the welding direction is confirmed, the main body part of the main hanging beam is welded on a displacement tool, the welding seam with the original welding position being PF is displaced to be a PB position, manual flanging of the main hanging beam is reduced, workload is reduced, and beam butt welding seam welding and beam fillet welding seam welding are carried out. The main hanging beam is symmetrically assembled on the displacement tool in a mode that a non-machining surface faces outwards, deformation of the displacement tool caused by welding deformation of the main hanging beam on one side is prevented, deformation exceeding scrapping caused by deformation of the displacement tool due to multiple accumulated deformation is avoided, the service life of the displacement tool is prolonged, the longitudinal beams on two ends are made into middle convex welding reversible deformation by using the displacement tool threaded pull rod, two main hanging beams are symmetrically welded in the welding process of the main hanging beams, and the influence of deformation of the main hanging beams on the displacement tool is reduced as much as possible on the premise of ensuring that deformation of the main hanging beams is reduced. In addition, a welding backing plate is additionally arranged on a fillet weld between the main hanging beam cross beam and the longitudinal beam, so that the weld penetration is ensured, the back side is prevented from being welded to form sagging, and the weld quality is greatly improved. The schematic diagram of the fillet weld between the cross beam and the longitudinal beam of the main hanging beam is shown in the attached drawing 2, and the structural schematic diagram of the welding backing plate is shown in the attached drawing 3.

The above embodiment can achieve the following beneficial effects:

(1) the embodiment of the invention adopts sub-process flow line operation, so that the single-process operation is simple, the duration is shortened, the process connectivity is enhanced, the production cycle is shortened, the working efficiency can be greatly improved, and the main hanging beam for finishing 1 workpiece by 6 riveters and 2 welders in 4 days originally is improved to finish 2 workpieces by 4 riveters and 2 welders in 4 days.

(2) According to the embodiment of the invention, the two ends of the two longitudinal beams are respectively reserved with 100mm post-welding machining allowance, the machining is carried out to the size required by a drawing in the post-welding integral machining process, the controllability of the integral outer contour of the main hanging beam is ensured, the influence of welding shrinkage on the total length is reduced, the accuracy of the total length of the longitudinal beams is improved, the total length tolerance of the longitudinal beams is controlled within +/-1 mm from +/-5 mm, and the integral outer contour tolerance is controlled within +/-2 mm from +/-6 mm.

(3) According to the embodiment of the invention, the main body welding process of the main hanging beam is placed on the deflection tool, the workload of artificial flanging is reduced, the welding position is easier to reach, the welding difficulty is reduced, the welding quality of the welding seam is ensured, and the one-time qualification rate of the vertical welding seam is improved from the unqualified inspection of one PT at four corners of each main hanging beam to the unqualified inspection of one PT at every 6 corners of each main hanging beam.

(4) The embodiment of the invention adopts the mode of reducing the action tolerance of the main hanging beam by the whole welding direction and the welding sequence, adjusting the welding discharge and the welding reversible deformation to reduce the dimensional tolerance of the main hanging beam, so that the dimensional tolerance of the length of the main hanging beam is adjusted to +/-3 mm from the original +/-7 mm; the width dimension tolerance is adjusted to +/-2 mm from the original +/-4 mm; the tolerance of the inner contour is adjusted to +/-3 mm from +/-5 mm; the adjustment time is shortened to within 2 hours by 2 riveters from about 1 day by 3 riveters.

(5) A special welding backing plate is added to the fillet weld between the main hanging beam cross beam and the longitudinal beam, so that the weld penetration is ensured, the back welding penetration is prevented from forming sagging, the weld quality is greatly improved, and the rework rate of the weld added with the special welding backing plate is reduced from 30% to 0 rework.

The invention controls the welding deformation of the main hoisting beam at the intercity of the sea: aiming at the characteristic that the requirement of a client on the welding seam is higher and higher. Because the requirement of welding seams is higher and higher, the welding difficulty is increased, the welding deformation is larger and larger, and the requirements of customer drawings on welding planeness, verticality and diagonal difference are higher. Therefore, through multiple experiments and demonstrations, a great deal of improvement work is performed on aspects of changing the welding sequence, adjusting the welding deformation, controlling the input of welding heat, improving the welding tool and the like, and through multiple improvements and practices of project groups, on the premise of ensuring the quality of a welding seam, the behavior tolerances such as the overall dimension, the planeness, the verticality, the diagonal difference and the like of the intercity car main hanging beam are well ensured, the adjustment amount of a line operator is effectively reduced, and the production efficiency is improved; the invention adopts the sub-process flow line operation, improves the working efficiency: because an intercity car owner hanging beam product is complicated, and parts are many, aiming at the characteristics of complex procedure, high requirement on skills of staff and long duration of a person who receives materials from a welding machine, prepares before welding, welds on a tool and performs inspection after welding, a sub-process flow line operation scheme is made after detailed argumentation and planning by project group organization related technologies, quality and manufacturing departments, the requirement on the skill comprehensiveness of workers is lowered, the training of a single process is enhanced, the operation of the single process of the workers is simplified, the duration is shortened, the process connectivity is enhanced, and the production period is shortened, thereby greatly improving the working efficiency and the productivity.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.