GB2232297A

GB2232297A - Part detecting device for part feeding units

Info

Publication number: GB2232297A
Application number: GB9009083A
Authority: GB
Inventors: Yoshitaka Aoyama
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-04-25
Filing date: 1990-04-23
Publication date: 1990-12-05
Also published as: DE4012918A1; KR900015849A; GB9009083D0; CN1046867A

Description

SPECIFICATION

PART DETECTING DEVICE FOR PART FEEDING UNITS BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to a device for detecting whether or not a part has been firmly held in place in a part feeding unit having a feeding rod adapted to hold a part and transport it to a predetermined destination.

Prior Art

In part feeding units of the type having a feeding rod adapted to hold a part and deliver it to a destination, it has been common practice to examine whether or not there is a part in a predetermined place. Among known methods therefor are one which utilizes the weight of a part to actuate a microswitch, and another which uses a phototransistor for such detection. However, since such precision parts as microswitches or phototransistors have to be attached to the feeding device, the construction is complicated and is influenced by foreign matter because of being precision parts. DISCLOSURE OF THE INVENTION

To solve the above problem, this invention is designed to detect the presence of a part by electric conduction between two parts which are obtained when part is held in the feeding rod. That is, as a result of a part being held in place in the feeding rod, the contact and electric conduction between the two make the electric circuit, thereby providing an electric signal signifying the presence of a part. Reversely, if the electric circuit is left open, this signifies that a part is not properly held, that is, there is an abnormality.

According to this invention, since a detection circuit is completed by contact between the feeding rod and a part, the employment of precision parts in the prior art can be avoided; thus, a highly reliable confirming function can be attained. Particularly, the effective use of the phenomenon in which the feeding rod and a part make direct contact with each other ensures the attainment of said effect.

An insulating element is fixed to the inner surface of an outer sleeve receiving the feeding rod and a slide plate for electric conduction to the feeding rod is attached to said insulating element so that the slide plate is kept in contact with the outer surface of the feeding rod all the time. Further, the insulating element may be in the form of a sleeve with the feeding rod extending therethrough. Being in the form of a sleeve provides improved support stability for the insulating element itself and allows a plurality of slide plates to be installed, greatly improving stability of electric conduction to the feeding rod. Since the insulating piece having the slide plate attached thereto is fixed on the inner surface of the outer sleeve, the support stability of the slide plate is improved and electric conduction to the feeding rod is always reliable. And by making the insulating element in the form of a sleeve through which the feeding rod extends, the supportability of the feeding rod is improved and a plurality of slide plates can be provided, whereby more reliable electrical conduction can be attained. If a pressing member which snugly fits in the opening in the outer sleeve is applied to the latter to fix the insulating element, the sleeve-like insulating element can be satisfactorily held in place; thus, firm support for the slide plate is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a longitudinal sectional view of a'part feeding unit having a detecting device embodying this invention; Fig. 2 is a bottom view of the unit of Fig. 1; Fig. 3 is a fragmentary longitudinal sectional view; Fig. 4 is an end view of a feeding rod; Fig. 5 is a fragmentary longitudinal sectional view; Fig. 6 is a fragmentary longitudinal sectional view; Fig. 7 is a sectional view taken along the line VII-VII in Fig. 6; Fig. 8 is a perspective view of an outer sleeve; Fig. 9 is a cross-sectional view showing a sleevelike insulating element; Fig. 10 is a side view of the Fig. 9 device, wherein is removed; and 12 are fragmentary longitudinal a presser plate Figs. 11 and sectional views.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figs. 1 and 2 show a part feeding unit of the type having a feeding rod 2 adapted to be inserted through the threaded hole of a nut 1 for feeding said nut. A part feeding pipe 3 of rectangular cross section is provided with an opening 4 disposed in the lower side and a temporary fixing chamber 5 disposed in the upper side at one end thereof. The right end of the temporary fixing chamber 5 is closed by a stop plate 6. An outer sleeve 7 is welded to the upper surface of the part feeding pipe 3 and houses the feeding rod 2. The feeding rod 2 is composed of a thin guide rod 8 adapted to extend through the threaded hole of the nut 1 and a main rod 9 thicker than said guide rod, with a push-out surface 10 defined in the interface between the rods 8 and 9. The feeding rod 2 is advanced and retracted by the output from an air cylinder 11 connected to the outer sleeve 7; thus, in this case, the piston rod of the air cylinder is the main rod 9. The upper surface of the part feeding pipe 3 is 1 1 formed with a through-hole 12 which is sufficiently large to allow passage of the main rod 9 therethrough, said through-hole being opposed to an insulating element 13. A magnet (permanent magnet) 14 is fitted in the stop plate 6, and the opposite sides of the stop plate are covered with protective plates 15 and 16. An arm 17 is welded to the outer sleeve 7 and has a bolt 18 screwed thereinto to urge the stop plate 6. The main rod 9 is constantly elastically contacted by a slide plate 19 serving as an electrical contact, said slide plate 19 being fixed to the outer sleeve 7 through an insulating element 20 with an electric wire 21 connected to the end of the slide plate 19 which projects outward. Another electric wire 22 is connected to the stop plate 6.

In Fig. 1, the nut 1 is temporarily locked in the temporary fixing chamber 5 in that it is attracted by the magnet 14, the feeding rod 1 being shown in the most retracted position. As the feeding rod 2 is advanced by the action of the air cylinder 11, the guide rod 8 extends through the threaded hole of the nut 1 until it reaches a certain position, whereupon the push-out surface 10 closely contacts the upper surface of the nut 1. Thereby, the current from the electric wire 21 flows from the feeding rod 2 via the nut 1 to the stop plate 6, making the circuit to the electric wire 22. Such closed circuit means that there is a nut 1 and that it is properly held in the feeding rod, confirming the normal state.

If the nut 1 should not lie in the temporary fixing chamber 5 for some reason or other, no current will flow between the electric wires 21 and 22 despite the advance of the feeding rod 2, a fact which means the presence of an abnormality. In this case, therefore, care is taken not to actuate any related machinery, e.g., a projection welding machine.

Figs. 3 and 4 show a modification, the difference from the preceding embodiment being that a nut 1 has a lid 23. In this case, since it is impossible for the guide rod to extend through the nut, as is clear from Fig. 4, the front end of the feeding rod 2 is bifurcated to form a pair of projections 24 and 25 so as to hold a nut 1 therebetween. The portion of the stop plate 6 which is to become the stop surface for the nut 1 has an insulating element 26 attached thereto. In the state shown in Fig. 3, the electric circuit has not been closed. However, when the feeding rod 2 is somewhat advanced, the nut 1 is separated from the insulating element 26 and comes in contact with the metal surface of the stop plate 6, so that a current flows between the electric wires 21 and 22. If the nut 1 fails to assume the illustrated position, an abnormality is confirmed immediately after the feeding rod 2 has advanced as in I the preceding embodiment.

In a modification shown in Fig. 5, the slide plate 19 is replaced by an insulating element 27 interposed between the outer sleeve 7 and the air cylinder 11 and an electric wire 21 is connected to the air cylinder 11. Therefore, electric conduction-is established between the electric wires 21 and 22 when the feeding rod 2 comes in contact with a nut 1.

A modification having a further improved construction for electric conduction will now be described.

In a modification shown in Figs. 6 and 7, a slide plate 24 is carried by an insulating piece 23 of arcuate cross section made of synthetic resin, said insulating piece 23 being fixed on the inner surface of the outer sleeve 7 by a bolt 25. Part of the slide plate 24 is force-fitted or molded in the insulating piece 23, and its portion projecting outside is elastically contacted with the main rod 9. The slide plate 24 is made from a copper alloy which is superior in elasticity and electric conduction, and has an electric wire 21 soldered thereto, as shown. An insulating sleeve 26 is fitted in a through-hole formed in the outer sleeve 7, and said electric wire 21 is led out through said insulating sleeve.

In a modification shown in Figs. 8 through 10, the insulating piece 23 is sleeve-like and is adapted to be inserted into an opening 27 formed in the outer sleeve 7 As shown in Figs. 9 and 10, a metal sleeve 28 is fitted in the sleeve-like insulating piece 23. A plurality of slide plates 24 extend integrally from one end of the metal sleeve 28 and elastically contact the main rod 9. A notch 29 is formed in the insulating piece 23 to expose the metal sleeve 28 for soldering an electric wire 21 thereto. The insulating piece 23 is inserted into the opening 27 and a presser member of arcuate cross section, that is, a presser plate 30 is fitted to the opening 27 in such a manner as to lid the opening 27, whereupon a fixing sleeve 31 put aside as shown in phantom lines in Fig. 8 is moved to cover the presser plate 30. Thereafter, a bolt 32 is screwed into the fixing sleeve 31 to urge the presser plate 30 to fix the insulating piece in place. In order to ensure that the urging force is applied reliably to the insulating piece 23, it is desirable to provide a clearance 33 between the outer sleeve 7 and the presser plate 30 so as to provide an pressing allowance.

Fig. 11 shows a modification wherein the outer sleeve 7 is internally provided with a step portion 34 engaged by a sleeve-like insulating piece 23, which is fixed in place by the tapered portion 36 of a bolt 35 applied from outside.

Fig. 12 shows a modification wherein a sleeve-like 1 insulating piece 23 is fixed in place by two bolts 37 and 38 applied from outside. The electric wire 21 is connected to the metal sleeve 28 through a bolt 39.

The above description has been centered on nuts; however, bolts may be fed by changing the shape of the part feeding pipe. The parts that can be handled are not limited thereto.

1

Claims

WHAT IS CLAIMED IS:

1. A part detecting device for part feeding units, wherein an electric circuit is closed by utilizing the fact that when a part is held by a feeding rod, it contacts the latter, thereby detecting the fact that the part has been normally held by the feeding rod.

2. A part detecting device for part feeding units as set forth in Claim 1, wherein an insulating piece is fixed to the inner surface of an outer sleeve which houses the feeding rod, and a slide plate for electric conduction to the feeding rod is attached to said insulating piece.

3. A part detecting device for part feeding units as set forth in Claim 2, wherein said insulating piece is a sleeve through which the feeding rod extends.

4. A part detecting devic for part feeding units as set forth in Claim 3, wherein a presser member is fitted to an opening formed in said outer sleeve and the fixing of said insulating piece is effected by said presser member.

5. A part detecting device for part feeding units, substantially as hereinbefore des.-::ribed with reference to the accompanying drawings.

Published 1990 at The Patent Office, State House. 66'71 High Holborn. LondonWCIR 4TP.Fu-ther copies mkybe obtainedfrom The Patent OfficeSales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray. Kent, Con. 1/87