1. Understanding Surveying and Mapping Objects
By observing the physical objects, reading relevant technical data and similar product drawings, we can understand its purpose, performance, working principle, structural characteristics and disassembly sequence. In the process of collecting data, we should pay special attention to the use and improvement opinions of production workers and technicians, and make full preparations for the smooth progress of surveying and mapping work. On the basis of a preliminary understanding of the function of the assembly, we can further understand the assembly and connection relationship between the parts by carefully analyzing the function and structure of the parts.
As shown in figure 10- 19, the valve core of the ball valve is spherical, which is used to open and close and adjust the flow. The valves in the positions shown in the figure are all open. When the wrench rotates 90 clockwise, all valves are closed.
The key part of assembly is the valve core, which is analyzed from the aspects of motion relationship, sealing relationship and containment relationship.
Kinematic relationship: wrench → valve stem → valve core.
Sealing relationship: two sealing rings are the first line of defense, and the adjusting pad not only ensures the sealing between the valve body and the bonnet, but also ensures the flexible rotation of the valve core; The second line of defense is packing to prevent fluid from leaking from the valve stem gap of rotating parts.
Inclusion: Valve body and bonnet are the main parts of ball valve, which are connected by four sets of studs. The valve core is positioned in the valve through two sealing rings, and the packing made of PTFE is fixed in the valve body through the packing compression sleeve and the threads of the valve body.
The left end of the valve body is connected with the valve cover through studs and nuts to form a cavity for accommodating the ball valve core. The cylindrical groove at the left end of the valve body is matched with the cylindrical flange of the valve cover. The cylindrical groove on the right side of the valve body cavity is used to place the sealing ring to ensure that the ball valve does not leak fluid when it is closed. The right end of the valve body is provided with an external thread connecting the pipeline in the system, and the internal stepped hole is communicated with the cavity. There is a stepped hole communicating with the cavity in the cylinder at the upper part of the valve body, and the valve stem, packing pressure sleeve and so on are installed in the stepped hole. The 90-degree fan-shaped limit bump at the top of the stepped hole is used to control the rotation angle of the wrench and the valve stem.
2. Disassemble the parts and draw the assembly drawing.
Before disassembly, prepare relevant disassembly tools, tools and places where parts are placed, and then make a careful disassembly plan according to the characteristics of assembly, and disassemble parts in a certain order. During disassembly, each part shall be numbered, registered and labeled. Dismantled parts should be grouped in appropriate places to avoid collision and deformation, so as to avoid confusion and loss, thus ensuring smooth reassembly.
Attention should be paid when disassembling parts: some necessary original dimensions should be measured before disassembling, such as the relative position between some parts. During disassembly, it is forbidden to knock at will to avoid damaging the original parts. For parts that can't be disassembled and connected, and have high-precision fit or interference fit, they should be disassembled as little as possible or not, so as not to reduce the original matching accuracy or damage the parts.
As shown in figure 10- 19, the disassembly sequence of the ball valve is as follows:
① Remove the wrench 13.
② Unscrew the packing press sleeve 1 1, take out the valve stem 12, and take out the packing 9 and packing pad 8.
③ Unscrew the nuts 7 connected with the four groups of studs with a wrench, and take out the valve cover 2 and the adjusting pad 5.
④ Take out the valve core 4 from the valve body to complete the disassembly.
Assembly sketch is a sketch that uses simple lines to draw the general outline of each part of the assembly body by visual inspection to show its assembly position, assembly relationship and working principle.
When drawing a schematic diagram, a part can be regarded as a transparent body, and its representation is not limited by the previous and subsequent levels. All parts should be represented on one diagram as far as possible. When drawing the schematic diagram of the transmission part of the mechanism, it should be drawn in accordance with the national standard "Symbol of Motion Diagram of Mechanical Drawing Mechanism". For general parts, the outline of the parts can be vividly drawn according to the shape and structural characteristics of the parts.
Fig. 10-20 ball valve assembly drawing
Drawing the assembly sketch should be done after a comprehensive understanding and analysis of the assembly, and in the process of disassembly, we should further understand the internal structure of the assembly and the relationship between parts, and make corrections and supplements, so as to draw the assembly drawing correctly and reassemble it in the future. The assembly drawing of the ball valve is shown in figure 10-20.
Sketch a part
Draw the removed parts one by one by hand. Some standard parts, such as bolts, screws, nuts, washers, keys and pins, can be omitted, but their main specifications and dimensions should be measured to determine their specified marks. Other data can be obtained by consulting relevant standards. All non-standard parts must be sketched, and the measurement dimensions are accurate and complete.
The drawing method of part sketch has been introduced before, and the following three points should be paid attention to when drawing part sketch in assembly surveying and mapping:
(1) The requirements for sketching parts are the same as those for drawing formal working drawings of parts, except that drawing lines is done by hand.
(2) Sketch the parts in sequence according to the assembly relationship or disassembly order, so as to proofread and coordinate the related dimensions between parts at any time.
(3) Dimensions related to the cooperation, connection and positioning between parts shall be coordinated and marked on the sketches of related parts.