US2696855A - Screw gripping jaw - Google Patents

Description

Dec. 14, 1954 www .fil

G. A. SEEGERS SCREW GRIPPING JAW i Filed Nov. 2. 1953 lll/Ill United States Patent O SCREW GRIPPING JAW Glen A. Seegers, Lombard, Ill., assignor to Illinois Tool Works, Chicago, lll., a corporation of Illinois Application November z, 195s, serial No. 389,779

7 Claims. (ci. 14432) This invention is concerned with a power screw driver, and more particularly with a screw catcher therefor.

Automatic power screw drivers as generally constructed in the past have not been entirely satisfactory. Most such power screw drivers have released screws by camming open the screw holders or catcher jaws by the screw heads as the screws are threaded into place by the driving plate. This has resulted in marring of the screw heads and in undue wear of the screw catchers. In many instances the screw catchers have had to abut the work piece, and this has resulted in marring of the work piece. Many prior power screw drivers have failed to retain screws satisfactorily in the catchers, and it has been extremely difficult or impossible to modify many power screw drivers for operation with different sizes and types of screws.

The general problems of the prior art were satisfactorily solved in the power screw driver disclosed by Leonard E. Austin in his Patent No. 2,646,091, issued July 2l, 1953. However, the screw catcher disclosed by Austin is of one-piece construction and is rather diiiicult to manufacture in that considerable care is necessary in selecting the material, in maintaining tolerances, and in heat treating the catcher. The unit construction of the Austin catcher somewhat limits the range of divergence of the catcher jaws, and the constant flexing of the catcher has been found in practice sometimes to lead to undesirably short operational life.

It is the general object of this invention to avoid the prior art difficulties as disclosed in the Austin patent, lvshile improving on the catcher mechanism disclosed by ustin.

More particularly, it is an object of this invention to provide an improved two-piece screw catcher in a power screw driver to prolong catcher life by eliminating flexing of the catcher.

Another object of this invention is to provide a twopiece screw catcher with a single spring bearing or acting equally on the two parts to assure symmetrical operation.

A further object of this invention is to provide a catcher for a power screw driver which is simpler to manufacture in allowing a wider selection of material, allowing greater tolerances, and in requiring less precise heat treatment.

Yet another object of this invention is to provide a screw catcher having a wider range of divergence.

Other and further objects and advantages of the present invention will be apparent from the following description when taken in connection with the accompanying drawings wherein:

Fig. l is a fragmentary side view of a power screw driver incorporating the principles of my invention;

Fig. 2 is a longitudinal sectional View through the catcher and associated structure;

Fig. 3 is a view similar to Fig. 2 showing the parts in a different position;

Fig. 4 is a perspective view of the screw catcher jaws;

Fig. 5 is a perspective view of the retainer ring and pivot pins; and

Fig. 6 is a top view partially in cross section showing the cooperation of the catcher jaws and retainer ring, and taken substantially along the line 6 6 of Fig. 3.

Referring first to Fig. l, there may be seen a portion of a power screw driver including a fixed cylindrical housing 10 and a fixed supporting arm 12 depending from a ring 14 affixed in any suitable manner to the bottom of the cylindrical housing 10. The housing 10 is suitably Patented Dec. 14, 1954 supported by a pedestal or the like, and those interested in further details may refer to Austin Patent 2,646,091 dated July 21, 1953. The depending fixed arm 12 adjustably carries a catcher control arm 16 by means of a suitable dovetail slide (not shown) and a clamping plate 18 having longitudinal flanges 20. The plate 18 is secured to the fixed arm 12 by bolts 22 and clamps the adjustable catcher control arm 16 against a dovetail seat (not shown) in the fixed arm 12.

The catcher control arm 16 is provided at its extremity with an offset portion 24 which integrally supports a sleeve or cylinder 26 in axial alignment with the cylindrical housing 10. The sleeve or cylinder 26 releasably mounts a thimble or bushing 28 having a radially outwardly projecting fiange 30 at the top end thereof. A spring wire 32 releasably locks the thimble or bushing in place as described in detail in the aforementioned Austin patent. The thimble or bushing acts to control the opening and closing of the screw catcher as will be apparent shortly.

The power screw driver further includes a cylindrical clutch housing 34 mounted for vertical reciprocation on a tube 36 depending from the housing 10 and vertically reciprocable relative thereto. A yoke 38 fits around the tube 36 and is a'iixed thereto for causing vertical reciprocation of this tube, the yoke, of course, being aixed to a suitable motor or actuator such as a pneumatic actuator. A clamping ring 40 is clamped about the tube 36 and is reciprocable therewith. A catcher lifter 42 is adjustably fixed to the arm 40 by means of a screw 44 fitting through an elongated slot 46 in the catcher lifter and threaded into the ring 46. A radially inwardly projecting tooth (not shown) on the bottom end of the catcher lifter 42 underlies a peripheral flange 48 at the top of the clutch housing 34 for lifting the same.

The flange 48 is provided with a beveled upper surface 56 which cooperates with a beveled surface or edge 52 on a catcher lowering arm 54 which is pivoted on the clamping ring 40 at 56. The beveled surface 52 comprises one edge of a tooth 58, which has an oppositely beveled edge 60. The catcher lowering arm 54 is provided on the side opposite the tooth 58 with a cam follower 62 having a rounded nose 64 engageable with a cam surface 66 on the control arm 16. The cam surface 56 is provided with a setback or shoulder 68. Thus, when the yoke 38 is forced down by the pneumatic or other actuator, the tubes 36 and 40 descend and the tooth 58 bearing against the flange 48 lowers the clutch housing 34 until the cam follower 62 reaches the setback or shoulder 68. This allows the tooth 58 to cam over the flange 48 so that the tube 36 continues to lower, while the clutch housing stops its descent, this position being limited by the flange 30 on the thimble 28 carried by the catcher control arm 16. When the yoke 38 is raised, substantially the reverse actions take place and the clutch housing 34 is raised by the inwardly projecting finger on the catcher lifter 42.

The catcher is located at the bottom of the clutch housing 34 and projects through the thimble 28. The catcher is identified generally by the number 70 and comprises a pair of arms 72 complementary to one another. The arms are provided at their bottom ends with inwardly directed retaining fingers 74, and are cut out thereabove as at 76 to permit transverse shifting of a screw into the catcher from a slide chute. The catcher arms are relatively thick for the major portion of their length from the bottom up, and are provided relatively near'the top thereof with shoulders 78 and a portion 80 of reduced diameter.

The catcher arms 72 are provided at their upper ends with a pair of semicircular plates 82 coacting to form a circular head 84. The plates are provided with chordal recesses 86 having upstanding ears or lugs 88 substan* tially at the diameters of the recess. The cooperating chordal recesses and lugs form a seat for a coil spring 90 which bears down against the head 84.

The catcher 70 is secured to the bottom of the clutch housing 34 by means of a clutch housing sleeve bottom 92 which is welded or otherwise suitably secured to the lower end of the clutch housing. The clutch housing sleeve bottom 92 comprises a cylindrical body portion 94 having a circumferential iiange 96 near the top thereof. The body portion lits part way into the clutch housing 34 with the flange abutting the bottom edge thereof. The clutch housing sleeve bottom 94 is provided with arcuately spaced, longitudinally extending bores 98 for reducing the weight of the part, and is also provided with an axial bore G provided with a shoulder 102 forming a seat for the spring 90. The spring 90 is formed of stock which is rectangular in cross section, and the opposite ends of the spring are ground flat for improved seating characteristics.

The outside of the clutch housing sleeve bottom is threaded as at 104 and a screw catcher nut 106 is threaded thereon. The screw catcher nut 196 is provided with an inwardly directed flange 108 along its lower edge which overlies and traps a retainer ring 111) having a pair of parallel, chordally disposed pivot pins 112 secured therein. Although the pivot pins may be secured by other means, I prefer to seat them in notches 114 in the ring, and to braze them in place. The pins 112 fit in chordal recesses 116 in the under sides of the plates 82 pivotally to mount the arms 72. The spring 9@ is compressed between the seat 1112 and the center of the head 84 formed by the plates 82. Since the spring presses on the plates between the pivot pins 112, it resiliently urges the arms 72 apart. This is resisted by the thimble 28 as will be brought out shortly.

A shank 118 extends up into the clutch housing 34 and carries at its lower end a screw driver 126. The screw driver is shaped to be complementary to the screw to be driven, and in the exemplary embodiment comprises a concave portion 122 and a driving blade 124 for complementary engagement with a round headed screw 126. The upper end of the shank 11S is connected to a suitable driving source such as an electric or pneumatic motor, and preferably is connected through suitable clutch means such as disclosed in the aforementioned Austin patent. Such clutch means preferably include a clutch which will release automatically upon the imposition of a predetermined maximum torque, and also a clutch which is normally disengaged, but which is engaged by the relatively upward thrust created by the engagement of the screw driver 12@ with a screw 124.

ln operation before lowering of the screw driving mechanism, the thimble 23 encircles the catcher arms 72 below the shoulders 78, i. e. around the relatively large part thereof. This holds the arms in slightly spaced, parallel relation as shown in Figs. l and 2. Screws are supplied to the catcher between the arms 72 and above the retaining ngers 74 transversely, preferably in proper timed relation from a screw feeding chute (not shown). Depression of the yoke 38 rst lowers the tube 36, and with it the shank 118 and screw driver 120 to cause the blade 124 to engage the driving slot of the screw. Continued depression of the yoke lowers the clutch housing 34 through the intermediary of catcher lowering arm 54 as previously noted. rThis drives the screw into the work piece 128 as shown in Fig. 3, and also moves the catcher arms 72 downwardly through the thimble 28. When the relatively small part 80 of the catcher arms passes into the thimble, the arms are free to spring apart under the force of the spring as shown in Fig. 3. This allows the screw driver 12? to drive the screw into fully seated position as shown in Fig. 3 without the necessity of the screw or driver camming the catcher arms 72 apart. Release or reverse action of the actuator (not shown) retracts the driver 120 into the space between the catcher arms 120, and the tooth of the catcher lifter 42 raises the clutch housing 34 and catcher 70 to their initial position wherein the catcher arms are held relatively toward one another for receipt and retention of another screw.

It will be seen that the multipiece catcher construction herein shown and described is simple and inexpensive to manufacture, and is relatively long-lived since the catcher arms themselves need not flex. Use of the two separate arms and the biasing spring provides for movement of the arms from substantial parallelism to a greater degree of divergence than is possible with integral arms.

The specific example disclosed herein is for illustrative purposes only, and it will be understood that the invention incorporates this and other embodiments insofar as they fall within the spirit and scope of the appended claims.

I claim:

l. In a screw catcher construction for power screw drivers, the combination comprising a pair of similar substantially rigid arms each having portions adapted to engage beneath a screw head to retain a screw by the head, members at the tops of the arms extending outwardly away from one another, pivotal mounting means received by said outwardly extending members outwardly of said arms, spring means pivotally biasing said arms away from one another, and means for controlling the divergence of said arms sequentially to retain and release screws for driving.

2. The combination set forth in claim 1 wherein the spring means comprises a single spring pressing on both pairs of said arms and outwardly projecting members.

3. The combination set forth in claim l wherein the spring means comprises a coil spring pressing axially on both of said projecting members between the pivotal mounting means.

4. ln a power screw driver having a depending cylindrical portion with external threads at the lower end thereof, means providing a spring seat generally within said cylindrical portion, a spring abutting said seat and extending downwardly axially of said cylindrical portion, a pair of catcher arms having outwardly projecting portions at the top ends thereof and at the bottom ends thereof adapted to seat a screw, said spring abutting said outwardly projecting portions, pivotal mounting means engaging said portions outwardly of said spring, and a retaining nut threaded on the external threads at the bottom of the cylindrical member, said nut forcing said pivotal mounting means upwardly radially of said cylindrical portion to cause said spring to bias said arms away from one another.

5. The combination as set forth in claim 4 wherein the pivotal mounting means comprise a ring and chordal pivot pins carried thereby, said ring being trapped by said retaining nut.

6. The combination set forth in claim 5 wherein the outwardly projecting portions on the arms are provided with downwardly opening chordal recesses for receiving said pivot pins.

7. The combination set forth in claim 4 wherein the external threads and the spring seat are provided on a plug secured to the bottom of said cylindrical portion.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,809,719 McWade June 9, 1931 2,175,299 Malvin Oct. l0, 1939 2,205,167 Greterman June 18, 1940 2,314,760 Blair Mar. 23, 1943 2,406,952 Iosepho Sept. 3, 1946 2,554,732 Doyle May 29, 1951 2,625,967 Stull Jan. 20, 1953 2,646,091 Austin July 2l, 1953 2,664,121 Travis Dec. 29, 1953

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