US3283791A

US3283791A - Automatic screwing device

Info

Publication number: US3283791A
Application number: US420625A
Authority: US
Inventors: Weber Karl
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-12-23
Filing date: 1964-12-23
Publication date: 1966-11-08
Anticipated expiration: 1983-11-08

Description

Nov. 8, 1966 K. WEBER AUTOMATIC SCREWING DEVICE 2 Sheets-Sheet 1 Filed Deo. 23, 1964 Fig. l

Fig3

Nov. 8, 1966 K, WEBER 3,283,791

AUTOMATIC SCREWING DEVICE Filed Dec. 23, 1964 2 Sheets-Sheet 2 United States Patent 3,283,791 AUTOMATIC SCREWING DEVICE Karl Weber, 51 Ulrichstrasse, 8021 Icking, Germany Filed Dec. 23, 1964, Ser. No. 420,625 10 Claims. (Cl. 144-32) The present invention relates to a screw-driving device to which the screws -are fed automatically for ea-ch operation, for instance by means of a vibrator in cooperation with a sorting device. This application contains subject matter disclosed in my copending application Ser. No. 402,754 filed October 9, 1964.

It is an object of this invention to proivde a screwdrivin-g device which will be able both to feed each screw individually into holding means and to drive the screw from said holding means into a work piece.

It is another object of this invention to provide a screwdriving device which will eject :a screw from the holding means if the screw, due to a manufacturing defect, for instance faulty thread 'or lack of the slot in the screw head, was not .screwed into the work piece.

Still another object of this invention consists in a device as set forth above, whi-ch is of a simple and reliable construction and is highly ecient in performance.

These land other 'objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIGURE 1 is a longitudinal section 'through a screwdriving device according to the present invention;

FIGURE 2 is a section taken along the line II--II of FIGURE 1;

FIGURE 3 illustrates on a larger scale than FIGURE 1 the lower portions of the screw-driver employed in the screw-driving device of FIGURE l;

FIGURE 4 illustrates a clamping device for use in connection with the screw-driving device according to the invention; and

FIGURE 5 shows the control mechanism for controlling the screw-driving device according to the present invention.

The screw-driving device according to the present invention is characterized primarily by two substantially axially aligned pistons recprocable in a cylinder common thereto yand operable by pressure fluid las, for instance, compressed air, said pistons being actuated successively. More specifically, each screw to be driven into a work piece is individually fed to one of said pistons which then moves the respective screw toward Ithe work piece whereupon the other piston displaces a screw-driver driving the respective screw into the work piece. After completion of the screw-driving operation, both pistons are returned to their starting position. The return of the pistons to their starting position may be effected by spring means which are loaded by the working stroke of the pistons, but advantageously, the pistons are designed as doubleacting pistons and are both advanced and returned by a pressure iluid medium,

The piston which moves the respective screw toward the work piece is advantageously so designed that its lower portion forms a tapered extension protruding from the cylinder common to both pistons. Provided 4in said eX- tension is a clamping device for receiving the respective screw. V

According to a further feature of the invention, the control of the pistons is such that the return movement of that piston which carries the screw-driver lags behind the other piston to such an extent that following an unsuc-cesful screw-driving operation, for instance in view of a faulty .screw or a faulty threaded bore in the work piece, the respective screw is ejected by the screw-driver 3,283,791 Patented Nov. 8, 1966` from the clamping device. The said screw is retained by the screw-driver until it drops out of the clamping device. It is only then that the piston which is connected to the screw-driver will effect the return movement. It will be appreciated that without this precautionary measure, jamming or damage may occur to the automatic feeding system, which damage not only causes considerable repair costs but will also necessitate a stoppage of the device for a considerable time.

The valves for the pressure iluid may be actuated by cams driven in cooperation with the drive for the shaft of the device, for instance may be controlled by a control shaft driven by an electric motor.

Referring now to the drawing in detail, the screw-driving device illustrated therein comprises a cylinder 1 having reciprocably mounted therein an upper piston 2 and a lower piston 3. Each of said pistons 2, 3 is designed as a double-acting piston, 'and is provided with shock- Iabsorbing

annular discs

2a, 2b and 3a, 3b respectively. Intermediate the annular discs 2a and 2b there is proivded an annular bottom 4 which is connected to the cylinder in any convenient manner, for instance by arresting pins 40, or is welded thereto. Similarly, intermediate the

annular discs

3a and 3b there is provided an annular bottom or disc 5' connected to piston 1 by pins 50. The cylinder 1 is provided with bores 6 and 7 on each side of ring member or bott'om 4, and similarly the cylinder 1 is provided with bores 8 and 9 on both sides of ring member 5. The bores 6 and 7 and correspondingly the bores 8 and 9 are, by means of pipe connections and valves to be described later, adapted to be connected alternately to a pressure fluid source or to an exhaust.

Provided in the upper piston 2 is a sleeve 10 which is journalled in antifriction bearings 11a and 11b so as to be rotatable relative to said piston 2. The lower end of sleeve 10 has, by means lof a :pin 15a, xedly connected thereto a screw-driver 15. Sleeve 10 is rotatably and aXially displaceably connected to a shaft 12 journalled in an anti-friction bearing 13 and drivingly connected lto a pulley 14. Pulley 14 may be driven by .a prime mover through a pulley belt connection, or in any other desired manner. The rotatable connection between shaft 12 and sleeve 10 may be effected in any standard manner, for instance by a groove and key connection or by a splined connection. According to a more advantageous arrangement which is illustrated in FIG. 2, shaft 13 has a square cross-section, and sleeve 10 is provided with a corresponding inner longitudinal bore of square contour. The wear and friction of this Ilast-mentioned arrangement is less than when employing a key and groove.

As will be seen from the drawing, lower piston 3 is provided with a conical extension 16 protruding from cylinder 1. This extension 16 has rotatably inserted therein an elastic conical clamping sleeve or chuck 17 which is provided with plurality of longitudinal slits (see FIG, 4). The clamping device may advantageously be composed of `a plurality of segments which are compressed by spring means. Morever, the lower portion of piston 3 has a recess 18 which is so contoured and dimensioned that the mouth of a screw `feeding pipe 19 maybe located above the bore of the clamping sleeve 17. Pipe 19 is by means of an elastic universal ball joint 20 connected to an intermediate member 21 while a pressure spring 21a continuously urges the pipe 19 into recess 18. Intermediate member 21 is connected to a pipe 22 for feeding `screws to the clam-ping means 17 while receiving the screws from a vibrator and a sorting device.

FIG. 5 diagrammatically illustrates the cotnrol mechanism for the screw driving device. An electric motor drives control shaft 101 through the intervention of a chain 102. One end of shaft 101 is provided with a worm 103 drivingly connected to a wor-m wheel 104 mounted on a shaft 105. Shaft 105 has detachably mounted thereon a plurality of

cams

106, 107, 108. These cams are adjustable relative to each other in order to make adjustments in conformity with the required operation of the screw-driving device. Cams 106 and 107 are adapted to control valves 109 and 110 through the intervention of pushrod rollers 111 and 112.

FIG. 5 illustrates the connections between the valves 109 and 110 and the bores 6, 7 and 8, 9 respectively. More specifically, conduits 115 and 116 respectively lead to the bores 8 and 6 yand bring about an upward movement of the pistons 3 and 2 respectively. On the other hand conduits 117 and 118 lead to the bores 7 and 9 and bring about a downward movement of the pistons 2 and 3 respectively. One revolution of the control shaft 105 results in one complete driving operation of the screwdriving device, i.e. each time the control shaft 105 has completed one revolution, one screw has been completely inserted into the work piece. The above-mentioned relative adjustability of the cams 106 and 107 affords t-he possibility `of varying the working rhythm of the driving device. Cam 108 is intended to serve for controlling a work piece feeding device known per se (not shown).

In order to rnake sure that the screws are not overlstressed and do not exceed the extent to which they are tightened, according to the .present invention a mechanically adjustable slip-clutch is inserted between the shaft 12 and the drive, for instance pulley 14.

More specifically, FIG. 5 shows a slip-clutch having a first portion 119 fixedly connected with shaft 101. Shaft 101 has slid-ably mounted thereon a sleeve 120. On sleeve 120 there are loosely journalled brake linings 121, 122 having located therebetween a pulley 123. Shaft 101 has furthermore mounted thereon a disc 124 and dish-springs 125 held in position by a disc 126 screwed onto the end of shaft 101. It should be noted that disc 124 is axially displaceable on shaft 101, however, not rotatable relative thereto. Inasmuch as disc 126 is axially adjustable on shaft 101 through the intervention of a thread 101a, spring 125 may be subjected to varying loads selected in conformity with the desired coupling ratio.

A belt 127 interconnects pulley 123 with pulley 14 of the screw-driver 15. It will be evident from the above that the clutch 119 to 126 determines the momentum exerted upon screw 23 in conformity with the adjustment of the clutch.

Operation For each working stroke, a screw 23 is fed into pipe 22, for instance by a sorting device, and the screw will, due to its own weight, advance in pipe 19 and drop into clamping device 17. Thereupon, valve 109 which controls the supply of pressure fluid through conduit 118 is opened so that the annular disc 3b of piston 3 will be acted upon by the pressure fluid, for instance compressed air. As a result thereof, piston 3 moves downwardly until clamping means 17 will be located directly above the threaded bore of the work piece (not shown). Piston 3 will temporarily remain in this position. Valve 110 which is located in the conduit 117 leading to bore 7 will now be opened and will thus convey pressure uid as, for instance compressed air, to t-he annular disc 2b of piston 2, so as to drive the same downwardly. During this downward ymovement of ypiston 2 the screw-driver 15 carried and advanced by piston 2, will displace feeding pipe 19 toward the right to such an extent that the screw-driver can unimpededly engage the screw head in clamping lmeans 17. The displacement of pipe 19 may, however, also be effected -by piston 3.

Due to the fact that the clamping means, for instance in form of the clamping sleeve 17, is rotatable, the screwdriver can easily and safely enter the slot in the screw head. Experience has shown that in this connection it is advantageous when the rotation of the clamping means 17 is effected with a certain amount of friction. For this reason, the clamping sleeve is journal-led in a friction bearing. Inasmuch as sleeve 10 rotatably connected to screw-driver 15 is rotated by pulley 14 through shaft 12, the screw-driver will rotate and, due to its simultaneous advancement by piston 2, will engage the screw and press the same through the resilient portion of the clamping sleeve 17 into the threaded bore of the respective work piece so that the screw is screwed into said bore. Screw-driver 15 is guided in sleeve 17 and cannot leave the slot in screw 23.

The respective `screw may hit upon the respective thread in the work piece at Vsuch a high speed that there exists the danger -of damaging the first thread winding of the screw and/ or the bore into which it is to be driven. In order to avoid this danger, sleeve 10 is in its antifriction bearings 11a and 11b displaceable over `a certain stroke against the thrust of a spring 24. Consequently, the degree to which the screw impacts upon the work piece will be cushioned and damage to the thread windings will, for all practical purposes, be impossible.

After the screw-driving operation has been completed, rst lower .piston 3 is returned to its starting position by means of pressure fluid such as compressed air conveyed through conduit 113, valve 109, conduit and bore 8. Subsequently, piston 2 is withdrawn but with such a time delay that a screw which could not be driven by screw-driver 15 into the respective bore, is retained until it is pushed out of the clamping device 17 by screwdriver 15 when piston 3 is lifted off the work piece. The magnitude of the delay may be selected by a corresponding relative angular adjustment of cams 106 and 107.

Inasmuch as also pipe 19, due to the effect of the elastic 'ball joint 20 and spring 21a, has returned to its starting position, the path for the next screw is freed, and a new screw can be conveyed to clamping device 17 Thus, the device is ready for a new cycle.

It may be mentioned that a number of reasons may cause an unsuccessful screw-driving operation. Thus, it may be that the screw or the bore in the work piece has accidentally not been provided with a thread, or that the screw head lacks a slot.

Furthermore, there exists the possibility that the re-y spective screw when dropping with its shank into the clamping device is located somewhat on a slant thereto. This -may be particularly true when employing short screws. The aligning or righting of the inclined screw is effected in a simple manner by slipping a tight-fitting sleeve 25 over the screw-driver end so that the screwdriver lblade 26 will protrude to an extent which corresponds to the depth of the slot in the screw head (see FIG. 3). When, during the downward movement of upper piston 2, the blade of the screw-driver catches the said slot of the screw head and enters the same, the screw will automatically-be righted by sleeve 25.

As will be evident from the above, any type of manual operation can be dispensed with when an automatic feed for the work pieces is employed. Furthermore, the device according to the present -invention is characterized by a high output per time unit. Inasmuch as the screwdriving device can be designed as a compact and time saving structure, it can be arranged and employed in numerous ways. Thus, for instance, depending on the respective requirements, a plurality of devices as descr-ibed above may be combined to a lsingle unit by means of which in one working stroke a plurality of screws can 'be driven into a work piece. v

It is, of course, to be understood, that the present invention is, by no means, limited to the particular arrangement shown in the drawing, but also comprises any modilications wit-hin the scope of the appended claims.

What I claim is:

1. In an automatic screw driving device: cylinder means, first fluid operable piston means reciprocable in said cylinder means, second fluid operable piston means arranged in substantially axial alignment with said first piston means and reciprocable in said cylinder means, said second piston means having an axial bore, sleeve means coaxially and rotatably arranged in said first piston means and axially movable therewith in either direction of movement of said first piston means, driving shaft means drivingly connected to said sleeve means for rotating the same, said sleeve means being axially displaceable relative to said driving shaft means, screw driver means connected to said sleeve means for rotation therewith, said screw driver means slidably extending into said axial bore of said second piston means and being movable from a rest position in a working stroke performing direction and to return to said rest position, and means associated with said cylinder means and operable to feed one screw at a time into said bore for engagement by said screw driver means during the movement of the latter in its working stroke performing direction.

2. In an automatic screw driving device: cylinder means, first piston means recipocable in said cylinder means, second piston means arranged in substantially axial alignment with said rst piston means and reciprocable in said cylinder means, said second piston means having an axial bore, sleeve means coaxially and rotatably arranged in said first piston means and axially movable therewith in either direction of movement of said first piston means, driving shaft means drivingly connected to said sleeve means for rotating the same, said sleeve means being axially displaceable relative to said driving shaft` means, screw driver means connected =to said sleeve means for rotation therewith, said screw driver means slid-ably extending into said axial bore of said second piston means and being movable by said first piston means in screw driving direction, and fluid operable means respectively associated with saidl first and second piston means for advancing and re-tracting the same, said second pist-on means being retractable prior to said rst piston means whereby a screw which remained in said bore during the movement of said screw driver means in its screw driving direction will be ejected from said bore.

3. An arrangement according to claim 1, in which said cylinder means is formed by a single cylinder common to said first and said second piston means.

4. A screw driving device according to claim 1, in which each of said first and second piston means is provided with two axially spaced oppositely effective surfaces, -and in which lone annular disc each is connected to said cylinder means intermediate the fluid operable sur- Yfaces of each of said first and said second piston means.

5. In an automatic screw driving device: cylinder means, rst uid operable piston means reciprocable in said cylinder means, second fiuid operable piston means arranged in substantially axial alignment with said first piston means and reciprocable in said cylinder means, said second piston means having an axial bore, sleeve means coaxially and rotatably arranged in said first piston means and `axially movable therewith in either direction of movement of said rst piston means, driving shaft means drivingly connected to said sleeve means for rotating the same, said sleeve means being axially displaceable relative to said driving shaft means, screw driver means connected to said sleeve means for rotation therewith, said screw driver means slidably extending linto said axial bore of said second piston means and being movable from a rest posi-tion in a working stroke performing direction and to return to said rest position, screw receiving and holding means arranged within said second piston means below and in spaced relationship to the free end of said screw driver means, and means associated with said cylinder means and operable to feed one screw at a time into said bore above said screw receiving and holding means for engagement by said screw driver means during the movement of the latter in its working stroke performing direction.

6. An arrangement according to claim 5, in which that portion of said second piston means which has said screw receiving and holding means therein protrudes from said cylinder means and tapers in a direction away therefrom.

7. An arrangement according -to claim 5, in which said screw receiving and holding means is frictionally rotatable in said second piston means.

3. In an automatic screw driving device: cylinder means, first fiuid operable piston means reciprocable in said cylinder means, second iiuid operable piston means arranged in substantially axial alignment with said first piston means and lreciprocable in said cylinder means, said second piston means having an axial bore, sleeve means coaxially and rotatably arranged in said first piston means and axially movable therewith in either direction of movement of said first piston means, driving shaft means drivingly connected to said sleeve means for rotating the same, said sleeve means being axially displaceable relative to said driving shaft means, screw driver means connected to said sleeve means for rotation therewith, said screw driver means slidably extending into said axial bore of said second piston means and being movable from a rest position in a working stroke performing direction and to return to said rest position, screw receiving and holding means arranged within said second piston 'means below and in spaced relationship to the free end of said screw driver means, said second piston means being `provided with a recess extending from the outside of said second piston means into the axial bore thereof, and tubular means having one section connected to said cylinder means and having another section elastically connected to said first section and adapted to extend through said recess means into said axial bore for feeding one screw at a time into said bore for engagement by said screwdriver means during the movement of the latter in its working stroke performing direction..

9. An arrangement according to claim 1, in which said driving shaft means is of a square cross section, and in which the sleeve means has its inner cross section shaped in conformity with the cross section of said driving shaft means.

10. An arrangement according to claim 1, in which said sleeve means has an axial extension in excess of the axial extension of said first piston means,I and in which spring means are interposed between one end of said pisfton means and the adjacent end of said sleeve means, said sleeve means being axially displaceable against the thrust of said spring means relative to said first piston means.

No references cited.

WILLIAM W. DYER, IR., Primary Examiner.

R. I. ZLOTNIK, Assistant Examiner.

Claims

5. IN AN AUTOMATIC SCREW DRIVING DEVICE: CYLINDER MEANS, FIRST FLUID OPERABLE PISTON MEANS RECIPROCABLE IN SAID CYLINDER MEANS, SECOND FLUID OPERABLE PISTON MEANS ARRANGED IN SUBSTANTIALLY AXIAL ALIGNMENT WITH SAID FIRST PISTON MEANS AND RECIPROCABLE IN SAID CYLINDER MEANS, SAID SECOND PISTON MEANS HAVING AN AXIAL BORE, SLEEVE MEANS COAXIALLY AND ROTATABLY ARRANGED IN SAID FIRST PISTON MEANS AND AXIALLY MOVABLE THEREWITH IN EITHER DIRECTION OF MOVEMENT OF SAID FIRST PISTON MEANS, DRIVING SHAFT MEANS DRIVINGLY CONNECTED TO SAID SLEEVE MEANS FOR ROTATING THE SAME, SAID SLEEVE MEANS BEING AXIALLY DISPLACEABLE RELATIVE TO SAID DRIVING SHAFT MEANS, SCREW DRIVER MEANS CONNECTED TO SAID SLEEVE MEANS FOR ROTATION THEREWITH, SAID SCREW DRIVER MEANS SLIDABLY EXTENDING INTO SAID AXIAL BORE OF SAID SECOND PISTON MEANS AND BEING MOVABLE FROM A REST POSITION IN A WORKING STROKE PERFORMING DIRECTION AND TO RETURN TO SAID REST POSITION, SCREW RECEIVING AND HOLDING MEANS ARRANGED WITH IN SAID SECOND PISTON MEANS BELOW AND IN SPACED RELATIONSHIP TO THE FREE END OF SAID SCREW DRIVER MEANS, AN D MEANS ASSOCIATED