TYPICAL ORIENTING SYSTEM

Of all the various types of feeding devices, vibratory-bowl feeders allow by far the greatest flexibility in the design of orienting devices. Figure 3.18 shows the FIGURE 3.17 Balanced vibratory feeder.

Inertia f orce Horizontal

component causes rocking

Rubber feet

(a)

(b)

Feed track

Springs Base

Recirculation of parts

Orienting devices

Part delivery

Springs

orienting system commonly employed to orient screws in a vibratory-bowl feeder.

In this arrangement, the first device, a wiper blade, rejects all the screws not lying flat on the track. The gap below the blade is adjusted so that a screw standing on its head or a screw resting on the top of others is either deflected back into the bowl or made to lie flat on the track. Clearly, the wiper blade can be applied here only if the length of the screw is greater than the diameter of its head. The next device, a pressure break, allows screws to pass only in single file and only with either head or shank leading. Screws being fed in any other attitude will fall off the narrow track and back into the bowl at this point. The pressure break also performs another function: If the delivery chute becomes full, excess parts are returned to the bottom of the bowl at the pressure break, and congestion in the chute is therefore avoided. The last device consists of a slot in the track that is sufficiently wide to allow the shank of the screw to fall through while retaining the screw head. Screws arriving at the slot either with the shank leading or with the head leading are therefore delivered with the shank down, supported by the head. In this system for orienting screws, the first two devices are passive and the last is active.

Although the devices described above are designed for parts of a certain shape, two of them have wide application in vibratory-bowl feeding. First, a pressure break is usually necessary because most feeders are adjusted to overfeed slightly in order to ensure that the workhead is never “starved” of parts. In this situation, unless a level-sensing device controlling the feeder output is attached to the delivery chute, the delivery chute is always full, and a pressure break provides a means of preventing congestion at its entrance.

Second, the wiper blade is a convenient method of rejecting parts that are resting on top of others. In a vibratory-bowl feeder, this often occurs because of the pushing action of parts traveling up the track. However, care must be taken in applying the wiper blade because thin parts may have a tendency to jam under FIGURE 3.18 Orientation of screws in vibratory-bowl feeder.

Slotted track

Bowl wall

Pressure break

Wiper blade

Screws rejected unless lying on side

Screws rejected unless in single file end-to-end or if delivery chute is full Slot in track

to orient screws To delivery

chute

the blade, as illustrated in Figure 3.19. The tendency for this jamming to occur can be reduced by arranging the blade so that it lies at an acute angle to the bowl, as shown in Figure 3.18. In some cases, an alternative approach is necessary, and this is illustrated in Figure 3.20, which shows the orienting device commonly employed to orient washers. It can be seen that a portion of the track is arranged to slope sideways and down toward the center of the bowl. A small ledge is provided along the edge of this section of the track to retain those washers that are lying flat and in single file. Other washers will slide off the track and into the bowl. With a device of this type, where the parts are rotated as they are fed, it is often necessary to arrange the design of the track to ensure that the path of the center of gravity of the part is not raised rapidly; otherwise, a serious reduction in feed rate may occur.

Figure 3.21 shows a refinement made in the orienting device described in the preceding paragraph. In this case, machined washers may be oriented by provid-ing a ledge sufficiently large to retain a washer beprovid-ing fed base down (Figure 3.21a) but too small to retain a washer being fed base up (Figure 3.21b).

Figure 3.22 illustrates a common type of orienting device known as a cutout, where a portion of the track has been cut away. This device makes use of the difference in shape between the top and the base of the part being fed. Because FIGURE 3.19 Thin parts jammed under wiper blade.

FIGURE 3.20 Orientation of washers in vibratory-bowl feeder.

Wiper blade Parts

Track

Bowl wall

To delivery chute

Ledge to retain washers lying flat on track

Washers not lying flat on track fall into bowl

of the width of the track and the wiper blade, the cup-shaped part can only arrive at the cutout resting on its base or on its top. It can be seen from Figure 3.22 that the cutout has been designed so that a part resting on its top falls off the track and into the bowl, whereas a part resting on its base passes over the cutout and moves onto the delivery chute.

Figure 3.23 shows another application of a cutout, in which the area covered by the top of a part is very much smaller than the area covered by its base. In this case, a V-shaped cutout rejects any part resting on its top.

FIGURE 3.21 Orientation of machined washers.

FIGURE 3.22 Orientation of cup-shaped parts in vibratory-bowl feeder.

(a) Washer accepted (b) Washer rejected

Scallop Bowl wall

Wiper blade

To delivery chute

Cutout rejects cup-shaped parts standing on their tops

Figure 3.24 shows an example in which U-shaped parts are oriented. With parts of this type, it is convenient to feed them supported on a rail. In this case, some of the parts climb onto the rail and pass to the delivery chute. The remainder falls into the bowl, either directly or through a slot between the rail and the bowl wall.

Figure 3.25 shows a narrowed-track orienting device that is generally employed to orient parts lengthwise end to end while permitting only one row to pass. Finally, Figure 3.26 shows a wall projection and narrowed-track device used to feed and orient parts with steps or grooves, such as short, headed parts.

FIGURE 3.23 Orientation of truncated cones in vibratory-bowl feeder.

FIGURE 3.24 Orientation of U-shaped parts in vibratory-bowl feeder.

V cutout

Bowl wall

Part rejected if resting on its top

To delivery chute

Wiper blade Rail

Bowl wall

To delivery chute

Parts rejected unless they climb onto rail

A short, headed part traveling on its larger end passes through the device, but other orientations are rejected back into the bowl.

Data on the design of orienting devices are presented in Appendix D.

FIGURE 3.25 Narrowed track.

FIGURE 3.26 Wall projection and narrowed track.

Bowl wall

To delivery chute

Narrowed track

Widthwise parts rejected while only one row of lengthwise parts pass

Wall projection and narrowed track

Wiper blade 30

Bowl wall

To delivery chute

Track width is set to reject all parts traveling on their smaller end

3.14 EFFECT OF ACTIVE ORIENTING DEVICES ON