Ball joints

The offset (O) needed to accommodate (c) depends on amount of allowable angular movement (0) in the ball joints used. (O) is measured as the distance between ball centerpoints of the joints. 

Except for smaller size joints, the nominal 0 for all ball joints is 15°. To avoid exceeding this angle, normal / actice h to increase 0 more than the actua minimum as a safety factor. 

Hinged Expansion Joints consist of one or more thin corrugated elements welded to short lengths 

The application of hinged expansion joints is especially useful when nozzle design loads are limited by the equipment manufacturer. Here is a list of conditions warranting consideration of hinged expansion joints. 

When the natural flexibility of the piping components cannot be used economically (supports, guides and directional anchors should be figured in the cost comparison) 

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The spherical joint or semi-ball joint or ball and socket joint is illustrated in Fig. 11, 55, 7, which includes one type of special clamp for holding the two halves of the joint together. This connexion cannot freeze... 

A metal stirrer must not be used. A simple glass stirrer with a ball-joint seal is satisfactory. 

In a 5-1. three-necked flask, fitted with a ball-joint sealed stirrer and a Soxhlet extractor (70 mm. internal diameter X 300 mm. length of body) carrying a large-capacity condenser, are placed... 

The apparatus consists of a 3-1. three-necked round-bottomed creased flask, with standard ball joints and an indented cone-shaped bottom (Note 1), which is heated by means of an electric mantle and is equipped with a high-speecT stirrer of stainless steel driven by a 10,000 r.p.m. motor (Note 2). One side neck is fitted with a bulb-type air-cooled condenser (Note 3), on top of which fits a 1-1. pressure-equalizing Hershberg dropping funnel (Note 4). The top of the dropping funnel is to be connected in turn to a U-tube containing a 1-cm. head of mercury. The entire apparatus is securely fastened to a sturdy support. 

The submitters used a ball-joint bearing. A mercury seal or a Trubore bearing should also suffice. 

In real life nodes are more complex than points, but various approximations to simple nodes can be built. These are often called pin joints, ball joints, or spherical joints- joints that can take axial loads, but caimot carry any torques. 

A convenient laboratory-scale storage device consists of a Schlenk tube (about 100 raL) with a Teflon valve in the side arm and a socket joint on top of the body of the tube. The stopper is the corresponding Teflon-seated ball joint attached to a small Teflon valve (Fig. 2), which allows the air in the space above the socket to be purged with nitrogen prior to closing the tube. The ball and socket joint is preferable to the common cone and socket arrangement because the metal oxide crust that invariably forms in the joint is more easily broken. 

The reaction vessels as shown in Figure 1 were cylindrical borosili-cate glass vessels, with i.d., 25 mm. and internal height, 36 mm. A standard-taper joint permitted connection to a stopcock. These two sections could be filled in a nitrogen atmosphere box. Then the sealed vessel could be connected to the vacuum system at the ball joint. 

A stirring assembly which makes use of a lubricated ball-joint seal3 is convenient. The checkers used a Hershberg stirrer rather than a centrifugal stirrer. 

A. Standard Taper and Ball Joints. These joints (Fig. 8.1) have been used for many years on vacuum and inert-atmosphere systems, and the availability of a variety of synthetic greases and waxes has extended their utility. Of the two, the ball-and-socket joint permits more flexibility in the orientation of the two halves. When this flexibility is important, this type of joint is obviously to be preferred, even though the ball joint is somewhat more prone to leak than a standard taper joint. Both metal ball joints and metal standard taper joints are available,1 and these items provide one means of joining metal and glass apparatus. 

Metal ball joints, metal standard taper joints, and O-ring joints with a step tooled into Ihe groove are available from Kontes Glass Co., P.O. Box 729, Vineland, NJ 08360. The first two items are also available from Ace Glass Co., P.O. Box 688, Vineland, NJ 08360. 

Fig. 9.19. Solvent storage container. Solvent is distilled in through the sidearm, which is then sealed off under vacuum. The container is attached to the vacuum line through a 18/9 ball joint or O-ring joint.

E. Miscellaneous Tubing Connectors. The variety of tubing couplers is enormous and a comprehensive list would be out of place in this book, but several additional types will be mentioned here which are useful in the laboratory. Metal standard taper and metal ball joints are available, and these will mate with corresponding ground-glass joints to provide one means of connecting parts made of dissimilar materials.4 As with glass standard taper joints, the seal is... 

Fig. 8.1. Standard taper ( ) and spherical joint ( ). When the joints are lubricated with grease, they must generally be held together. Springs or rubber bands arc frequently employed on standard taper joints, while a spring-loaded clamp (illustrated here) or a screw clamp (illustrated in Fig. 8.3) is used with ball joints. The method used for specifying joint sizes in the United States is illustrated, and it is described in detail in National Bureau of Standards, Commercial Standard CS 21-39.

In a dry-box, a magnetic stirring bar and 32.3 g. (0.242 mole) of aluminum chloride, A1C13, are placed in a 500-ml., round-bottomed flask fitted with a 35/25 ball joint. The capped flask is removed from the dry-box and quickly attached to an addition funnel containing ether under low nitrogen pressure ( -l p.s.i.). 

The spherical or semi-ball joint is shown in Fig. 2.6 which includes one type of special clamp for holding the two halves of the joint together. This connection cannot freeze or stick (as conical joints sometimes do) and it introduces a degree of flexibility into the apparatus in which it is used. The area of contact between the ground surfaces is relatively small so the joints are not intended to provide for considerable angular deflection. The main application is in conjunction with conical joints rather than as a substitute for them. The conical-spherical adapters shown in Fig. 2.7 provide a means of inserting a spherical joint while retaining the conical joint principle. 

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