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CHAPTER
1
General Introduction to Drawing
Different Drawing Views
Orthogonal Views
Perspective Views
Variations of a Perspective View
Perspective Foreshortening
No Foreshortening Versus Excessive Foreshortening
Realistic Foreshortening
Drawing With Pen, Ruler, and Instruments
Necessary Tools
Pen and Ruler Drawing Techniques
Drawing With a Computer
Equipment
Computer Drawing Techniques
Using a Camera
Equipment
Taking Pictures
Tracing Pictures
Summary
This chapter provides the background information you need to understand the more advanced concepts that are presented in later chapters. Basic drawing principles, including the different types of drawing views and foreshortening (a technique for making realistic views), are presented here. We also provide an overview of several drawing methods, to show you that making patent drawings is probably easier than you may have anticipated.
Different Drawing Views
Any physical object can be seen from a great variety of view anglesâfor example, head-on, from the side, from the top, and from the back. Of course, a single drawing, also known as a drawing view or a figure, may show an object only from one view angle. Typically, a single figure cannot show all of the important features or parts of an object, because some of them may be on an opposite side that is not visible in the view. Therefore, when you need to clearly explain the structure of an invention in a patent application, several drawing views may be necessary to show the object from different angles.
Certain view angles have conventional names, so that they can be immediately understood when referred to. Letâs look at the most common of these views.
Orthogonal Views
An orthogonal, or right-angle (engineering), view is one in which the viewerâs eyes are centered over a particular side of the object. Put another way, the viewerâs line of sight is perpendicular to such side. A special objectâespecially created to look different from every sideâis shown in perspective at the top of Illustration 1.1 and is shown below the perspective view in all possible orthogonal views, as described here.
Front Side or Front Elevational View. Shows the front side from a viewpoint centered over the front side.
Rear Side or Rear Elevational View. Shows the rear side from a viewpoint centered over the rear side.
Right Side View or Right Elevational View. Shows the right side from a viewpoint centered over the right side.
Left Side View or Left Elevational View. Shows the left side from a viewpoint centered over the left side.
Top Side View or Plan View. Shows the top side from a viewpoint centered over the top side.
Bottom Side View. Shows the bottom side from a viewpoint centered over the bottom side.
Orthogonal views are relatively difficult to understand because they do not convey a sense of depth, so the shapes of many surfaces appear ambiguous. Despite such a shortcoming, orthogonal views are commonly used in patent drawings because they are relatively simple to make, and are usually already available if the item is being manufactured. If one of the orthogonal views is considered alone, without the benefit of the other views, the true shape of the object cannot be deciphered. Such ambiguity is shown in Illustration 1.2. An object that appears as a rectangle in an orthogonal view may have many possible true shapes. Therefore, if an orthogonal view does not convey the shape of an object clearly enough, it should also be shown in one or more perspective views.
Perspective Views
A perspective view is one that shows the three dimensions of an object on a two-dimensional surface; it is not orthogonal to or centered over any side. When the view angle is properly selected, it presents an object as it would be seen in real life by a casual observer. It conveys a good sense of depth, so that it is much easier to understand than orthogonal views. The special object of Illustration 1.1 is shown in typical perspective views in Illustration 1.3, which includes those described below.
Illustration 1.1âOrthogonal Views
Illustration 1.2âOrthogonal View May Be Ambiguous
Illustration 1.3âPerspective Views
Front Perspective View. Shows the front side somewhat angled away.
Rear Perspective View. Shows the rear side somewhat angled away.
Right Perspective View. Shows the right side somewhat angled away.
Left Perspective View. Shows the left side somewhat angled away.
Top Perspective View. Shows the top side somewhat angled away.
Bottom Perspective View. Shows the bottom side somewhat angled away.
Variations of a Perspective View
If the two sides of an object are equally visibleâfor example, the top and frontâthen it may be called either a top perspective or a front perspective view. The view angle of any particular perspective view may be varied. Using the same special object of Illustration 1.1, some variations on the front perspective views are shown in Illustration 1.4, including those described below.
Front Perspective View (from above). Shows the front from a higher viewpoint off to one side.
Front Perspective (from the same level). Shows the front from a viewpoint off to one side, but at the same level. Such a view is almost as ambiguous as the front orthogonal view, so it is not recommended.
Front Perspective (from below). Shows the front from a lower viewpoint off to one side.
Illustration 1.4âVariations of the Same Perspective View
Illustration 1.5âIsometric View
Illustration 1.6âExploded View
Illustration 1.7âSectional View
One particular type of perspective view is the isometric (iso = equal; metric = measurement) view, from which the viewerâs eyes or viewpoint are positioned exactly between three orthogonal views, as illustrated by the simple cube in Illustration 1.5.
Letâs look at two other types of drawing views.
Exploded View. The parts of a device can be disassembled and spread apart in space to show otherwise hidden features, as pictured in Illustration 1.6, a water pipe fitting. Exploded views may be orthogonal or perspective. For example, there can be a front exploded view, a side exploded view, and so on.
Sectional View. Part of an object can be sliced away to show interior structures. Sectional views may also be orthogonal or perspective. For illustration, there can be a front sectional view, a side sectional view, a front perspective sectional view, and so on. The view shown in Illustration 1.7 is a side perspective sectional view of the water pipe fitting of Illustration 1.6.
Perspective Foreshortening
In real life, objects in the distance appear smaller than similar objects up close. The same principle also applies to a single, three-dimensional object: Its far end appears smaller than its near end, and its parallel edges appear to converge. The closer you are to the object, the greater the ...
