US3586230A

US3586230A - Riveting machine

Info

Publication number: US3586230A
Application number: US811782A
Authority: US
Inventors: F Leroy Hill; Burton A Rolland; James R Stamm
Original assignee: Hill Rockford Co
Current assignee: Hill Rockford Co
Priority date: 1969-04-01
Filing date: 1969-04-01
Publication date: 1971-06-22
Anticipated expiration: 1988-06-22

Abstract

This riveting machine has a reciprocating pneumatic riveter head located below the work table. Its pneumatic piston, carrying a peen, is rotated by an electric or pneumatic motor for spinimpact riveting. This head is mounted on a slide which is raised vertically to operating position in timed relation to corresponding downward movement of an anvil which backs up the head of the rivet. The workpieces are positioned on a pilot pin, which retracts when the rivet is inserted through the holes of the workpieces and then moves aside to made way for the riveting head to move up into position and form the rivet. The rivets are fed into spring-pressed jaws which move with the anvil and hold the rivet by its shank until it starts entering the workpieces at which point the jaws are opened and their movement stopped while the anvil moves down to press the rivet through the workpieces. The pilot pin is held in position by a spring or small air cylinder so valved that when the rivet presses against it, retraction of the pin is accomplished by the air cylinder. A cam on the slide holding the riveter head moves the pilot pin and air cylinder to one side for the riveting operation. The movement of the anvil is accomplished by an air cylinder and when the anvil has pushed the rivet through the workpieces, a horizontal wedge is moved by an air cylinder into a slot in the anvil producing a final movement forcing the rivet and workpieces tightly together and furnishing a solid backing for the anvil. Upon completion of the riveting operation, the riveting head and anvil retract and the pilot pin automatically returns to its original position with the pin projecting through the table. The sequence of operations is started by a foot switch or valve.

Description

United States Patent [72] Inventors F. Leroy Hill;

Burton A. Rolland; James R. Stamm, all of Rocklord, Ill. 121] App]. No. 811,782 [22] Filed Apr. 1,1969 [45] Patented June 22, i971 [73] Assignee Hill-Rockford Co.

Rockford, Ill.

[54] RlVETlNG MACHINE 35 Claims, 15 Drawing Figs.

[52] U.S.Cl 227/51 [51] lnt.Cl....I B2lj 15/10 [50] Field olSearch 227/51,6l, 62

[56] References Cited UNlTED STATES PATENTS 2,101,924 12/1937 Tumquist 227/51 X 2,156,167 4/1939 Snyder etal.. 227/62 2,230.518 2/1941 Weinhold..... 227/61 2,442,949 6/1948 Fischer 227/62 3,030,833 4/1962 Siegal etal 227/61 Primary ExaminerGranville Y. Custer, .lr.

Attorney-Andrew F. Wintercorn ABSTRACT: This riveting machine has a reciprocating pneumatic riveter head located below the work table. lts pneumatic piston, carrying a peen, is rotated by an electric or pneumatic motor for spin-impact riveting. This head is mounted on a slide which is raised vertically to operating position in timed relation to corresponding downward movement of an anvil which backs up the head of the rivet. The workpieces are positioned on a pilot pin, which retracts when the rivet is inserted through the holes of the workpieces and then moves aside to made way for the rivetinghead to move up into position and form the rivet. The rivets are fed into spring-pressed jaws which move with the anvil and hold the rivet by its shank until it starts entering the workpieces at which point the jaws are opened and their movement stopped while the anvil moves down to press the rivet through the workpieces. The pilot pin is held in position by a spring or small air cylinder so valved that when the rivet presses against it, retraction of the pin is accomplished by the air cylinder. A cam on the slide holding the riveter head moves the pilot pin and air cylinder to one side for the riveting operation.

The movement of the anvil is accomplished by an air cylinder and when the anvil has pushed the rivet through the workpieces, a horizontal wedge is moved by an air cylinder into a slot in the anvil producing a final movement forcing the rivet and workpieces tightly together and furnishing a solid backing forthe anvil.

Upon completion of the riveting operation, the riveting head and anvil retract and the pilot pin automatically returns to its original position with the pin projecting through the table.

The sequence of operations is started by a foot switch or valve.

PATENTEUJUNEZISH 3586.230

SHEET 1 OF 5 lNVENTORS F. LEROY HILL BURTON A. ROLLAND JAMES R. STAMM I 3 a Attornev PATENTEDJUHZZIHYI 3,586,230 SHEET 2 UF 5 INVENTORS F LEROY HILL pmmmmueenam 3.686230 SHEET 3 OF 5 L 85 84 F/ EX- PATENTEDJUN22|97| 5 2.

' sum 5 BF 5 ADVANCE ADV D RET ADV D F. LEROY HlLL BURTON A. ROLLAND JAMES R. STAMM I Attorney RIVETING MACHINE This invention relates to pneumatic riveting machines utilizing reciprocating motion of a piston to supply the required number of blows to complete each riveting operation, this type of riveter being generally classified as a spin-impact riveter.

The principal object of our invention is to provide a riveter of unique design, departing considerably from traditional design with a view to gaining certain advantages never heretofore attained, the present riveter incorporating the following new features:

I. The riveter head operates from below the work instead of the conventional arrangement above the same, thereby enabling rivets to be fed to the work from above while hanging by their heads, which is the most advantageous arrangement during transfer;

2. A pilot pin for centering rivet holes in the work with respect to the rivet enters the rivet holes from below and is retractable downwardly to guide the rivet into the hole as it is inserted in the opening step of the riveting cycle;

3. The pilot pin retracting mechanism under the work supporting table operates in timed relation with an elevating riveting head so that the latter comes into operative position with respect to the work as the pilot pin is forced to retracted position by the rivet;

4. An anvil for backing up the rivet during the riveting operation has, cooperating with it, a wedge block operated by a piston and cylinder mechanism in timed relation to the retraction of the pilot pin and insertion of the rivet, and

5. A novel self-starting feature is incorporated in the riveting head which allows full retraction of the piston after each riveting operation by virtue of a novel port arrangement and cylinder construction, an important feature being that under no circumstances can the piston hammer on either end of the bore of the cylinder, there being an air cushion provided in both ends of the cylinder preventing such hammering, the port arrangement and special construction of the piston and cylinder enabling use of the piston and cylinder assembly with either end up so that it can be used in the conventional manner above the work table and is not limited to use as herein shown below the work table.

The invention is illustrated in the accompanying drawings, in which:

FIGS. I and 2 are a side view and front view, respectively, of a riveting machine made in accordance with our invention;

FIG. 3 is a section on the line 3-3 of FIG. 2, illustrating the anvil and wedge block feature with the parts shown in retracted position ready for the start of a riveting cycle;

FIG. 4 is related to FIG. 3 showing the parts in their other extreme position after the rivet has been inserted and the pilot pin retracted, the rivet being solidly backed up by the anvil and wedge block for the upsetting of the projecting end of the rivet;

FIG. 5 is a section through the piston and cylinder assembly taken on the line 5-5 of FIG. 2 showing the piston in retracted position;

FIG. 6 is a section on the line 6-6 of FIG. 5 showing the piston in a middle or operating position;

FIGS. 7, 8 and 8A are diagrammatic illustrations of the piston and cylinder assembly with the piston shown at rest in FIG. 7 and in operation in FIG. 8, similarly as in FIGS. 5 and 6, respectively, while FIG. 8A shows the piston in its upper position, where compression of air in the cushioning chamber above the piston prevents hammering on the end cap;

FIG. 9 is a plan view of the work table taken on the line 9-9 of FIG. 2 with a portion of the table broken away to show parts in elevation therebeneath;

FIG. 10 is a front view of FIG. 9;

FIG. I] is a section on the line II11 of FIG. 9;

FIG. 11A illustrates a modification of the retractable pilot pin mechanism;

FIG. 12 is an electrical circuit diagram for the small number of parts of the machine operated electrically, and

FIG. 13 is a pneumatic circuit diagram for the machine.

The same reference numerals are applied to corresponding parts throughout the views.

Referring to the drawings, attention is first called to the piston and cylinder assembly 14, as seen in FIG. 1 and 2 but shown in more detail in FIGS. 5 to 8. The construction appears in FIG. Sand 6, but its mode of operation is best understood from the diagrammatic FIGS. 7 and 8. Compressed air is admitted through port 15 to the bore I6 of the cylinder 17 in which the piston 18 is reciprocable to reciprocate the rivet upsetting punch 19. During its reciprocation, the piston 18 also is given rotation of about rpm. by a spindle 20 that has a square head 21 slidable in a square bore 22 provided in a bushing fixed in a bore in the piston 18, as shown in FIG. 5, the spindle 20 having a driving connection with the armature of an electric motor 23 mounted on the lower end of the cylinder I7. The cylinder 17 has two

exhaust connections

24 and 25. The motor 23 may, of course, be operable pneumatically, like piston 18, for example. The piston 18 gravitates to the down position shown in FIGS. 5 and 7 after a riveting operation is completed. Compressed air entering port 15 cannot raise the piston 18 from its down position shown in FIGS. 5 and 7 until air entering port 26 past the check valve 27 is supplied through the annular groove 28 and a radial passage 29 in the piston and through a longitudinal passage 30 opening to the lower end of the piston 18. From there on it is the larger volume of air through port 15 that causes the piston to reciprocate as air supplied through passage 31 causes downward motion and air supplied through passage 32 causes upward motion,

ports

24 and 25 in this operation serving their purpose as exhaust ports. It is important to note that in normal operation, the piston operates at midlevel between the opposed

end cushion chambers

33 and 34 that are provided at opposite ends of the bore 16, so that under no circumstances can the piston 18 hammer on either end of the bore 16, there being an air cushion afforded at both ends as seen at 33 and 34 in FIGS. 5 and 6 preventing'such hammering.

The operation, more specifically stated, is as follows:

The riveter head 14 heretofore referred to as the piston and cylinder assembly, is carried on a slide 35 (FIG. 2) secured as at 36 to the upright frame 37 below the work table 38, in coaxial relation to retractable pilot pin 39 and the outer end of its pivoted carrier bracket 40. The latter is swingable out of the way of the upsetting tool 19 and head I4 in timed relation to the upward movement of the upsetting tool 19 with the piston 18 at the beginning of a riveting operation. The head 14, incidentally, is operable in any plane and with either end up, by virtue of the novel piston and cylinder construction and port arrangement including an elongated cutout at X on the piston 18 which plays no part in the present operation but is necessary in the inverted condition. The head is herein disclosed with the piston 18 operable upwardly from below the work table 38, so that the piston 18 in the absence of air pressure admitted to the inlet port 15 rests on the cap 41 due to the force of gravity. Hence, assuming piston 18 is in that position, as in FIGS. 5 and 7, when compressed air is supplied to port 15, piston 18, as seen in FIG. 7, has the inlet port closed so that the compressed air must be delivered through port 26 in the end cap 42 to the port 29 in the piston through the annular groove 28 in the end cap and then through longitudinal passage 30 to the bottom cushion chamber 34 to force the piston 18 slowly upwardly. The piston 18 continues to rise until the annular groove 43 in the piston allows a larger volume of air to pass from the inlet port 15 through port 32 and passage 44 and port 45 to chamber 34 under the piston, whereupon the piston rises quickly until the lower edge 46 of the piston opens the exhaust port 25, relieving the air pressure under the piston. In the meantime port 32 has been closed and port 31 has been opened to groove 43 so that compressed air from the inlet port 15 is delivered through port 31, passage 46 and port 47 to chamber 33 above the piston to start the downward movement of the piston. Momentum of the piston may cause it to travel upwardly to the point of momentarily closing the port 47, but the air trapped in chamber 33 cushions the operation preventing hammering of the piston against the end cap 42. Compressed air passing through reopened port 47 forces the piston 18 downwardly until the upper edge of the groove 43 closes the port 31, and the upper edge of the piston opens the exhaust port 24, whereupon the incoming air then passes through groove 43, port 32, passage 44, and port 45 to chamber 34 to start the piston moving upwardly againrHere again momentarily, the momentum of the piston may cause the lower edge 46 to close the port 45, but the air trapped in the chamber 34 prevents hammering on the lower end cap 41. It is possible that the pressure of the trapped air will become higher than the air pressure through port 26, overpower it, and thereby destroy the necessary cushion to overcome the momentum of the piston. Hence, we either provide the check valve 27, that is spring-pressed outwardly, as shown in FIGS. 7 and 8, or reduce the port diameter sufficiently so that airflow is throttled enough to maintain the necessary cushioning action. Of course, the back and forth movement of the piston required for the upsetting operation with the tool 19 continues as long as air is supplied to the inlet port 15. It isn't considered necessary to describe the cycle of operation with the piston 18 operating an upset tool downwardly from above a work support as that arrangement does not coincide with the present disclosure and it is therefore considered sufficient to state that the present piston and cylinder construction and port arrangement does permit such operation; I

Referring next to FIGS. 1 to 4 and 9 to 11, 48 in H68. 1 and 2 designates a foot-operable switch that is depressed by the operator to start a cycle, which will now be outlined, A rivet 49 (FIG. 4) is fed from feeder 50 down a track 51, hanging by its head with its shankextending downwardly from the longitudinally extending slot 52 in the bottom of the feeder track, to a transfer device 53 that includes a piston movable horizontally in a cylinder 54 and operated by compressed air. The spring-pressed jaws 55 of the placement and anvil device 56 are in line with the ends of the feed track 51 and, at the beginning of the cycle, are held open slightly for easy transfer of the rivets against spring pressure between the jaws 55 by the aforesaid piston, the transfer device 53 being designed to transfer only one rivet from the feed track at a time into the jaws 55 of the device 56. The two or more pieces of the work indicated at 57 in H6. 4 as resting on the table 38 with the rivet holes 58 in vertically aligned relation are adapted to receive the shank of the rivet 49 eventually after the work is placed on the table 38 with the pilot pin 39 entered therein to maintain proper relationship of the work pieces until the shank of the rivet has been entered through the registering holes 58. The foot switch 48 is depressed by the operator at the start of the cycle, whereupon the cylinder 59 of devices 56 has compressed air delivered thereto through pipe 60 so that the piston 61, that is connected by the T-head 62 to the diametrically extending flat extension 63 of the ram 64, lowers the ram 64 against the resistance of the spring 65. The jaws 55 close firmly on the shank of the rivet, as in FIG. 3, at the com mencement of downward movement of ram 64 with the anvil 66 that is provided on the lower end of the ram 64. Downward movement of ram 64 continues until anvil 66 is disposed with its cupped lower end 67 bearing on the rounded head of the rivet, as seen in FIG. 3, very slight endwise movement of the reduced lower end portion 68 of the ram relative to the jaws 55 being enough to close these jaws because they are pivoted at 69 intermediate their ends and are normally urged to closed position by compression springs 70 and have adjustable screws 71 extending inwardly therefrom on the other side of the pivots 69 have the ends of these screws ride into the annular recess 72 behind the larger radius portion 73 on which the screws 71 were riding previously. ln other words, screws 71 keep the jaws S separated enough for entry therebetween of the shank of the rivet, but thereafter allow the jaws to close on the rivet enabling lowering of the anvil 66 with the jaws 55 closed until the lower end of the rivet 49 contacts the upper end of the pilot pin 39 and depresses it in the further downward movement of the rivet. Just before the jaws 55 reach the work, the sleeve 74 on which the jaws 55 are mounted, is stopped by engagement of the nut 75 (FIG. 2) with a stop projection 76 provided on one side of the housing 77 in which the bore 78 is provided for the sleeve 74 and ram 64, so that the ram 64 can continue on its way downwardly independently of the sleeve 74 to the final extreme position shown in FIG. 4, where a wedge block 84, which serves to make certain that the work 57 and rivet 49 are backed up adequately during the upsetting of the lower end of the shank of the rivet by the tool 19, is in wedging engagement with the upper end of the ram. The spring 79, so long as spring 65 holds ram 64 in its fully retracted position shown in FIG. 3, keeps the portion 73 of the reduced portion 68 of the ram in the position shown in FIG. 3 with jaws 55 slightly separated as required for the insertion of a rivet against the resistance of springs 70 but the instant the ram 64 is given any downward movement, spring 79, in view of the lost motion between ram 64 and sleeve 74, retards the sleeve 74 enough in relation to the ram 64 for the ends of screws 71 to drop into the recess 72 and thus cause the jaws 55 to close under action of springs 70 on the rivet 49, holding the rivet firmly up to the point where the anvil 64 starts pushing the pilot pin 39 downwardly out of the work 57, and entering the shank of the rivet 49 into the rivet holes 58 in the work, the jaws 55 being then suddenly forced apart as the stop nut 75 engages the stop projection 76 on housing 77, stopping the sleeve 74 and allowing ram 64 to move downwardly relative to the sleeve so that the screws 71 ride up onto the largest portion 68 of the lower end of the reduced portion 68 of the ram. The screw 80, with respect to which the stop nut 75 is adjustable, is mounted on a plate 81 that is fixed to and movable with sleeve 74, this screw working freely in a hole in the stop projection 76. Housing 77 is carried on a plate 82 fastened, as indicated at 83, to the frame 37. i

The wedge block 84 of cylindrical form is guided in a bore 85 in right angle relation to and intersection the bore 78 provided for the ram 64 and has the forked outer end portion 86 of its wedge-shaped end 87 movable from the retracted position, shown in H6. 3, to the operative position, shown in FIG. 4, where the forked portion 86 straddles the reduced end portion 63 of the ram 64 with its inclined bottom surface 87 wedgingly engaging the inclined top surface 88 on the ram 64, thereby giving solid support to the anvil 66 during the riveting operation by tool 19. Wedge block 84 is held against turning in the bore 85 by its T-shaped connection 89 with the piston 90, the enlarged outer end of which is reciprocable in the horizontal pneumatic cylinder 91. The wedge 84 is, of course, operated in timed relationship to the operation of the ram 64, so as to move into wedging relation ship to the ram after the latter has reached its lower extreme position, shown in FIG. 4, and, of course, the wedge block 84 will be retracted before the ram 64 is retracted.

Referring next to FIGS. 9 to 11 along with FIGS. 1 and 2, the retractable pilot pin 39, which is of the same diameter as the shank of the rivet 49 and is therefore adapted to be entered with a working fit in the registering holes 58 in the work pieces 57 when the operator places the work on the table 38 prior to depressing the pedal. operated switch 48 to start a riveting cycle, is mounted in a plunger 92 reciprocable in a vertical bore 93 provided in the outer end of a swingable carrier bracket 40 that is provided on the underside of the table 38, as shown at 94 in FIGS. 9 and ll. The coiled compression spring 95 urges the plunger 92 upwardly so as to extend it into a bore 96 that is provided in the bottom of the table 38 and registers with the bore 93 in bracket 40 when the bracket 40 is in its operative position, shown in full lines in FIG. 9. An annular shoulder 97 provided in the upper end of the bore 96 in the table 38 limits the upward movement of the plunger 92 with the flange portion 98 on the pilot pin 39 lying flush with the top of the table so that the work pieces can be stacked on the pilot pin before the riveting operation is commenced. A coiled tension spring 99 attached at one end to the underside of the table 38, as seen in FIG. 9, and at the other end to a projection 100 provided on one side of the bracket 40 normally holds the bracket in the operative position abutting a stop 101 provided on the underside of the table 38. However, when the piston 18 of the head 14 is raised toward its operative position under air pressure, as previously described, to bring the upsetting tool 19 into operative relationship to the projecting lower end of the rivet shank, as seen in FIG. 4, a roller 102 carried on the lower end of the projection I00 comes into engagement with a cam 103, that moves with the piston 18 and tool 19, as shown in FIG. 10, so as to force the bracket 40 out of the way, as seen in dot-and-dash lines in FIG. 9, the shank of the rivet 49 having just prior to this engaged the pilot pin 39 and forced it downwardly with the plunger 92 against the action of spring 95 far enough to permit the lateral swinging movement of the bracket 40just mentioned. An arcuate groove 104 provided in the underside of the table 38 provides working clearance for the upper end of pilot pin 39 and as much of the plunger 92 as has not been lowered to the plane of the bottom of the table 38. A setscrew 105 that secures the shank of the pilot pin 39 to plunger 92 is accessible from in front of the table 38 through a hole 106 when the bracket 40 is in its operative position. This permits changing the pilot pin when a different size rivet is to be used in a different run of work. Of course, when the pilot pin 39 has been retracted fully and moved with the bracket 40 to an out-of-the-way position there is nothing to interfere with the riveting tool 19 moving all the way to its operative position in riveting engagement with the projecting end of the shank of the rivet, the riveting tool 19 operating then centrally of the bore 96 in the table 38, in coaxial relationship to the rivet 49, so as to upset the projecting end of its shank against the bottom of the work. The riveting operation of tool 19 is continued as long as its timer T shown in FIG. 12 permits.

The small amount of electrical control equipment involved with the motor 23 and foot-operated switch 48, as diagrammed in FIG. 12, is housed along with pneumatic control equipment, illustrated diagrammatically in FIG. 13, in a cabinet 107, a portion of which is shown in FIG. 2, as mounted on one side of frame 37 on a piano-type hinge 108 so as to be swingable laterally to an open position whenever access to equipment in the cabinet is required.

Next, referring to FIGS. 1, 2, l2, and 13, the sequence of operations is as follows: The operator, after placing the workpiece 57 on the work table 38 with the pilot pin 39 entered in the rivet holes 58, depresses foot switch 48, indicated diagrammatically in FIG. 13, to start the cycle. Pilot section 109 is pressurized and anvil 66 with a rivet 49 loaded in the jaws 55 from the previous cycle advances downwardly with the ram 64 until limit switch 110 is operated, after the rivet 49 has forced the pilot pin 19 to retracted position, entering the rivet all the way in the rivet holes in the work. Then the pilot section 111 is pressurized and the wedge block piston 90 advances the wedge block 84 until limit switch 112 is operated, which is when the block has wedging engagement on the inclined top surface 88 of the ram 64 to back up the anvil 66 solidly for the riveting operation. By virtue of the length of the wedging interengagement it is obvious that there is ample compensation for whatever minor differences in dimension may occur with different rivets from any given batch and even compensate for whatever differences in dimension there may be in successive sets of workpieces 57 assembled on the pilot pin 39 in any given production run. The lower end of the rivet shank is now projecting below the workpieces in the opening 96 in the work table 38 ready for the upsetting of the rivet against the bottom of the work, and at this point pilot section 113 is pressurized so that the riveting tool 19 is advanced with piston 18 until limit switch 114 is operated, which is when the tool has moved all the way from a fully retracted position to its operativeor riveting position, the tool 19 being, of course, also turned by virtue of electric motor 23 throughout the upsetting operation. Cam 103 engages bracket 40 as the riveting tool 19 is raised, moving the bracket out of the way for the duration of the riveting operation. Pressure switch 115 (FIG. 12) is closed at this point and the length of the riveting operation is predetermined by the electrical timer T to be certain of a complete riveting operation in each cycle. As soon as the riveting is completed pilot section 116 is pressurized and solenoid 117 is energized and the piston 18 returns to its lower position, whereupon limit switch 118 is operated. At the same time, pilot section 119 is pressurized, causing the piston 90 to be retracted so as to retract the wedge block 84 from behind the ram 64, whereupon limit switch 120 is operated. Then pilot section 121 is pressurized, causing retraction of the ram 64 with the piston 61 until limit switch 122 is operated, thus completing the cycle, except for the loading ofa rivet between the jaws 55 by advancement of the piston in cylinder 54, this piston returning thereafter to end the cycle. In this final operation, pilot section 123 is first pressurized to supply air to one end of the cylinder 54 until limit switch 124 is operated, after which pilot section 125 is pressurized to supply air to the other end of the cylinder 54 to return the piston, limit switch 126 being finally operated at the end of the cycle.

It is possible also to operate the riveting machine by manual control, as, for example, for setup and service work, by setting switch 127 (FIG. 12) at 128 for manual" instead of at 129 for automatic, the switch 127 being shown in off" position. Closing switch 127 in either position energizes solenoid 130 to turn the air logic on. The cycle for manual control is started also by the operator depressing switch 48, but from there on the operation is automatic again except for no timing of the riveting operation. Riveting continues until the operator depresses return" button 131.

In automatic operation, should there be a miscue on the part of the rivet feed mechanism, or should the rivet supply run out, in either of which cases there is no rivet in front of the anvil to engage and depress the pilot pin 39, to retracted position, the operator will be alerted at once when the machine jams by reason of the cam 103 striking the immovable carrier bracket 40. He then merely depresses the return button 131 to get all parts of the machine back to their starting positions and, of course, remedies the trouble that caused the jam before starting a new cycle. No damage is done to the machine or the work in such an emergency. I

Referring now to FIG. 11A and the dotted lower portion of FIG. 13, the retractable pilot pin 39, which is here shown as carried on an air pressure operated piston 132 reciprocable in a cylinder 133 oscillatable horizontally to and from operative position with a carrier bracket 40 similarly as in FIG. 11, the piston 132 being normally held raised by air delivered through the lower flexible hose 134 and port 134 until the pin 39' is forced down by the rivet about one-sixteenth inch when it is being inserted in the rivet holes in the work by downward movement of the anvil as described above. In this slight depression of the pilot pin, the piston 132 uncovers a port 135 in the wall of the cylinder 133, previously covered by the piston, so air is delivered through flexible hose 136 to the cylinder above the piston 132 to force it down to the lower end of the cylinder, retracting the pilot pin fully so that there is nothing to interfere with the pushing aside of the cylinder and retracted pilot pin therein by the cam 103 engaging the carrier bracket as previously described as the riveting head moves up to operative position. Later, when the wedge 84 is being retracted at the end of the cycle and the bracket 40 swings back to operative position as the riveting head is being retracted, air pressure through tube 134 raises piston 132 to extend the pilot pin 39 again to its operative position for loading of work again on table 38. This air retracted and air extended pilot pin 39 requires very little addition to the air circuitry, as appears in dotted lines in FIG. 13, where it is shown how the

tubes

134 and 136 are connected up with the wedge block operating mechanism to pressurize cylinder 133 automatically at the end of each cycle to advance the pilot pin 39 to operative position. With this construction, as with the other, the operator is immediately alerted in the event of the absence of a rivet as by the rivet supply running out, because the pilot pin 39' is in such event not depressed the small extent necessary to cause its retraction by air pressure, so the machine jams when the cam 103 rises with the riveting head and strikes the immovable carrier bracket, when the operator need only depress the return button 131 to get back to the starting point of a new cycle and no damage is done to the machine or the work.

It is believed that the foregoing description conveys a good understanding of the objects and advantages of our invention. While a preferred embodiment of the invention has been illustrated and described, this is only for the purpose of illustration, and it is to be understood that various modifications in structure will occur to a person skilled in this art.

We claim 1. A riveting machine comprising, in combination, an upright frame having a substantially horizontal work table on which work pieces to be riveted together are placed with rivet holes in register, means for feeding rivets one-by-one head up downwardly to the work from above the table with the shank of the rivet in vertically aligned relationship to the rivet holes in the work and through the rivet holes and into a hole provided in said table, the lower end portion of the rivet shank being exposed in said hole provided in the work table so that its projecting portion may be upset against the bottom of the work, the rivet feeding means including anvil means above the table engaging the head of the rivet to prevent its upward displacement during a riveting operation, a riveting tool disposed below said table aligned with the hole therein and the lower end of the rivet shank, a piston vertically disposed in coaxial relationship with the riveting tool, and a pneumatic cylinder in a fixed spaced relation to and below the work table on the frame, said cylinder having said piston reciprocable therein and extending from the upper end thereof and connected with the riveting tool, the cylinder having a source of compressed air connected therewith for reciprocation of said piston during a riveting operation.

2. A riveting machine as set forth in claim I, wherein said cylinder has the source of compressed air connected thereto intermediate the ends thereof, said cylinder having air cushion chambers at the upper and lower ends thereof in the form of closed extensions of its bore of the same diameter as the piston ends in which air is trapped and subjected to compression behind the piston when it projects therein and which by entry of the piston ends therein prevent hammering on either end of said cylinder by said piston.

3. A riveting machine as set forth in claim 2, wherein said cylinder has exhaust and other ports interrelated with the intake port and at least the bottom cushion chamber whereby not only is hammering of the piston on either end of the cylinder prevented due to the air cushion chambers, one of which also prevents bottoming of the piston in the lower end of the cylinder, but the piston upon turning on of air to the cylinder after a stoppage will rise to a mid level by air supplied to the bottom cushion chamber in the cylinder and will thereafter reciprocate between the two air cushion chambers throughout the riveting operation.

4. A substantially vertical air cylinder and piston assembly that is self-starting from a standstill, said assembly comprising a substantially vertical cylinder having a piston reciprocable therein, said cylinder having an air cushion chamber at least in the lower end thereof in the form of a closed extension of its bore of the same diameter as the piston end preventing bottoming of the piston therein by compression of air trapped by the piston in said chamber when the operation is stopped and the piston gravitates partway into and seals said chamber, said cylinder having a source of compressed air connected to an inlet port intermediate its ends for reciprocation of said piston, said cylinder also having exhaust and other ports interrelated with the intake port and the bottom cushion chamber, whereby the piston upon turning on of the air to the cylinder after a stoppage will rise to a midlevel by air supplied to the bottom cushion chamber in the cylinder and will thereafter reciprocate until the air is shut off again.

5. A piston and cylinder assembly as set forth in claim 4,

.wherein said cylinder also has an air cushion chamber like the other cushion chamber in the upper end thereof for compressing air trapped by the piston when entered partway therein, said cushion chambers preventing hammering by the piston against either end of said cylinder.

6. A piston and cylinder assembly as set forth in claim 5, wherein said assembly by virtue of the air cushion chambers in both ends and the port arrangement establishing communication substantially the same way between the intake port and the other ports and said cushion chambers is operable substantially alike with either end ofthe cylinder uppermost.

7. In a riveting machine, an upright frame having a substantially horizontal work table carried thereon in which an opening is provided, a pilot pin slidably guided vertically in said opening from below said table, a support for said pin movable laterally relative to the bottom of said table to and from a retracted position but normally held under spring pressure in an operative position with the pin disposed in said opening and projecting upwardly from said table and adapted to have workpieces with rivet holes provided therein stacked by means of their rivet holes on said pin preparatory to being riveted together, said pin being retractable into said support against yieldable resistance means, a riveting tool in aligned relation to said opening and carried on and reciprocable upwardly to said table and downwardly away from it with a part working in a substantially vertical guide carried on said frame below said table, an anvil arranged to engage the head of a rivet from above said table for backup support of said rivet during a riveting operation, a ram carrying said anvil and movable downwardly toward said table and upwardly away from it in aligned relation to said riveting tool and also carrying spring-pressed jaws adapted to carry arivet with its head end up in front of said anvil so as to engage the pilot pin and force it downwardly out of the rivet holes in the work as the shank of the rivet enters the rivet holes and until the pilot pin is fully retracted below said table, means for feeding rivets one by one between said jaws, means causing opening of the jaws when the rivet enters the rivet holes in the workpieces, means operable in timed relation to the upward movement of said riveting tool to force said pilot pin support with said pin fully retracted therein to a retracted position out of the way of the riveting tool permitting riveting of the workpieces together by upsetting the lower end of the rivet entered in the work, and power means for reciprocating the riveting tool carrying part in a riveting operation.

8. A riveting machine as set forth in claim 7, including means positively supporting said anvil against upward displacement by the rivet during the riveting operation.

9. A riveting machine as set forth in claim 7, including means positively supporting said anvil against upward displacement by the rivet during the riveting operation by wedging engagement with the upper end of said ram.

10. A riveting machine as set forth in claim 7, including a wedge clock slidable in a guide transversely relative to said ram to have wedging engagement with a portion of said ram for positively supporting said anvil against upward displacement by the rivet during the riveting operation, and power operable means for reciprocating said wedge block in timed relation to the reciprocation of said ram to move to operative position after its downstroke and be retracted before its return stroke.

1 l. A riveting machine as set forth in claim 7, wherein said pilot pin support comprises a bracket pivoted at one end in a fixed relationship to the underside of said table and having said pilot pin slidably mounted in the other end and normally urged yieldably upwardly relative thereto.

12. A riveting machine as set forth in claim 7, wherein the means for retracting said pilot pin support comprises a cam moving upwardly with the riveting tool and arranged to cam said pilot pin support laterally out of its way before the riveting tool arrives at the rivet to upset the lower end thereof.

13. A riveting machine as set forth in claim 7, including motor operated means connected for spinning said riveting tool during the riveting operation.

14. In a riveting machine, an upright frame having a substantially horizontal work table carried thereon in which an opening is provided, a pilot pin slidably guided vertically in said opening from below said table, a support for said pin movable laterally relative to the bottom of said table to and from a retracted position but normally held under spring pressure in an operative position with the pin disposed in said opening and projecting upwardly from said table and adapted to have workpieces with rivet holes provided therein stacked by means of their rivet holes on said pin preparatory to being riveted together, said pin being retractable into said support against yieldable resistance means, a riveting tool in aligned relation to said opening and carried on and reciprocable upwardly to said table and downwardly away from it with a part working in a substantially vertical guide carried on said frame below said table, an anvil arranged to engage the head of a rivet from above said table for backup support of said rivet during a riveting operation, means for feeding rivets one by one head end up vertically disposed in front of said anvil, means for moving said anvil downwardly to press a rivet downwardly against the top of the pilot pin to force it downwardly out of the rivet holes in the work so as to enter the shank of the rivet until the pilot pin is fully retracted below said table, means operable in timed relation to the upward movement of said riveting tool to force said pilot pin support with said pin fully retracted therein to a retracted position out of the way of the riveting tool permitting riveting of the workpieces together by upsetting the lower end of the rivet entered in the work, and power means for reciprocating the riveting tool carrying part in a riveting operation.

15. A riveting machine as set forth in claim 14, including means positively supporting said anvil against upward displacement by the rivet during the riveting operation.

16. A riveting machine as set forth in claim 14, including means positively supporting said anvil against upward displacement by the rivet during the riveting operation by wedging engagement with the upper end of said ramv 17. A riveting machine as set forth in claim 14, including a wedge block slidable in a guide transversely relative to said ram to have wedging engagement with a portion of said ram for positively supporting said anvil against upward displacement by the rivet during the riveting operation, and power operable means for reciprocating said wedge block in timed relation to the reciprocation of said ram to move to operative position after its downstroke and be retracted before its return stroke.

18. A riveting machine as set forth in claim 14, wherein said pilot pin support comprises a bracket pivoted at one end in a fixed relationship to the underside of said table and having said pilot pin slidably mounted in the other end and springpressed upwardly relative thereto.

19. A riveting machine as set forth in claim 14, wherein the means for retracting said pilot pin support comprises a cam moving upwardly with the riveting tool and arranged to cam said pilot pin support laterally out of its way before the riveting tool arrives at the rivet to upset the lower end thereof.

20. A riveting machine as set forth in claim 14, including motor operated means connected for spinning said riveting tool during the riveting operation.

21. A riveting machine comprising, in combination, an upright frame having a substantially horizontal worktable on which workpieces to be riveted together are placed with rivet holes in register, means for feeding rivets one by one head up downwardly to the work from above the table with the shank of the rivet in vertically aligned relationship to the rivet holes in the work and through the rivet holes and into a hole provided in said table, the lower end portion of the rivet shank being exposed in said hole provided in the work table so that its projecting end portion may be upset against the bottom of the work, the rivet feeding means including anvil means above the table engaging the head of the rivet to prevent its upward displacement during a riveting operation, a riveting tool disposed below said table aligned with the hole therein and the lower end of the rivet shank, a piston vertically disposed in coaxial relationship with the riveting tool, a pneumatic cylinder in a fixed spaced relation to and below the worktable on the frame, said cylinder having said piston reciprocable therein and extending from the upper end thereof and connected with the riveting tool, the cylinder having a source of compressed air connected therewith for reciprocation of said piston during a riveting operation, and motor operated means connected for spinning said riveting tool during a riveting operation.

22. A riveting machine as set forth in claim 21, wherein the motor has a housing in fixed relation to said cylinder, and its rotor has a rotary spindle driven by and extending from said rotor into said cylinder relative to which said piston is reeiprocable, said piston and spindle having a slip connection, whereby rotation is transmitted to said piston during its reciprocation.

23. In a riveter, the combination of a work support having an opening provided therein over which the work rests on said support, a riveting tool and an anvil in coaxially aligned relation to one another opposite sides of said support at said opening, the anvil being adapted to engage the head of a rivet inserted in registering holes in the work and the riveting tool being adapted to upset the projecting end of the shank of said rivet against the work, said anvil being movable to and from operative relationship to the rivet in a guide, a wedge block reciprocable in transverse relationship to said guide to and from wedging engagement with a portion of said anvil to support the latter against outward displacement relative to the rivet during a riveting operation, the wedging relationship of the wedge clock to the anvil being of sufficient length to allow for differences in rivets, means for moving the anvil to and from operative position, means for moving the wedge block to and from operative position in timed relationship to the movement of said anvil, and means for reciprocating the riveting tool.

24. In a riveter, the combination of a work support having an opening provided therein over which the work rests on said support, a riveting tool and an anvil in coaxially aligned relation to one another below and above said support at said opening, the anvil being adapted to engage the head of a rivet inserted in registering holes in the work and the riveting tool being adapted to upset the projecting end of the shank of said rivet against the work, said anvil being movable to and from operative relationship to the rivet in a guide, a wedge block reciprocable in transverse relationship to said guide to and from wedging engagement with a portion of said anvil to support the latter against outward displacement relative to the rivet during a riveting operation, the wedging relationship of the wedge block to the anvil being of sufficient length to allow for differences in rivets and differences in dimensions of work being riveted, means for moving the anvil to and from operative position, means for moving the wedge block to and from operative position in timed relationship to the movement of said anvil, and means for reciprocating the riveting tool.

25. In combination, a cylinder having a bore therein, a piston reciprocable in said bore and also rotatable, said piston having a rod coaxial and rigid therewith and extending through and closing a central opening provided in one end of said cylinder for connection with a part to be reciproeated and turned simultaneously, said piston having an axial bore provided therein, a motor the housing of which is coaxial and connected with and closes the other end of said cylinder, a rotor rotatable in said motor housing in coaxial relation to said piston, and a drive spindle coaxial with said piston and armature and connected at one end with said armature to have drive transmitted therefrom, said spindle having itsother end slidably but nonrotatably connected with said piston in the axial bore thereof to transmit drive thereto from said armature.

Y 26. The combination, as set forth in claim 25, wherein the sliding nonrotary connection is a loose one allowing compressed air to pass freely longitudinally through said piston in moving said piston from a retracted position in said cylinder to an operating zone where said piston is reciprocable.

27. In a riveting machine comprising an upright frame supporting a work table having an opening provided therein, riveting mechanism below said table operable in the opening, anvil mechanism over said table adapted to bear downwardly against the head ofa rivet inserted in rivet holes in workpieces placed on said table over said opening, whereby to prevent upward displacement of said rivet during the upsetting of its lower end against the bottom of the work, a pilot pin projecting upwardly relative to said table from said opening prior to the riveting operation for mounting of the workpieces on the table by engagement in the rivet holes from below, and means under said table supporting said pilot pin for retraction therein when a rivet is entered in the rivet holes from above replacing said pin, said pilot pin supporting means being shiftable to an out of the way position with the pin in retracted position to permit operation of said riveting mechanism in said opening.

28. A riveting machine as set forth in claim 27, including spring means whereby said pilot pin supporting means is normally urged toward operative position, there being means movable with said riveting mechanism for shifting said supporting means to an out of the way position as the mechanism moves toward operative position relative to said table.

29. A riveting machine as set forth in claim 27, wherein said pilot pin supporting means comprises an air cylinder with a piston reciprocable up and down therein and carrying said pilot pin thereon, and air supply means communicating with either end of said cylinder whereby said piston is movable upwardly under air pressure to hold said pin in extended operative position or is movable downwardly under air pressure to retract said pin,

30. A riveting machine as set forth in claim 27, wherein said pilot pin supporting means comprises an air cylinder with a piston reciprocable up and down therein and carrying said pilot pin thereon, and air supply means communicating with either end of said cylinder whereby said piston is movable upwardly under air pressure to hold said pin in extended operative position or is movable downwardly under air pressure to retract said pin, the structure including means whereby downward movement of said pin a predetermined distance by entry of a rivet in the rivet holes to a predetermined extent reversing the air operation of said piston so it moves downwardly and retracts said pin.

31. In a riveting machine, the combination of a worktable on which workpieces to be riveted together are placed with rivet holes in register with an opening provided in said table, rivets being inserted downwardly in the rivet holes head end up, an anvil guided for downward movement in alignment with ment in transverse relation to said anvil and arranged to have wedging engagement with said anvil when the latter is in engagement with the head of a rivet, whereby positively to prevent upward displacement of the rivet during the riveting operation.

32. in a riveting machine, the combination of a work table on which workpieces to be riveted together are placed with rivetjholes in register with an opening provided in said table, rivets-being inserted downwardly in the rivet holes head end up, an anvil guided for downward movement in alignment with the opening in said table from above the same for engagement with a rivet head to prevent upward displacement of the rivet during a riveting operation, a pilot pin carried on and retractable into a support movably mounted under said table for movement to a retracted position relative to said table opening, said pilot pin engaging through the opening in said table in the rivet holes in said workpieces but arranged to be retracted when a rivet entered in the holes in the workpieces comes into engagement with said pilot pin whereby to render said pilot pin support retractable, a power-operated riveting tool below said table in vertical alignment with and arranged to operate through the table opening to upset the projecting lower end portion of a rivet upwardly against the bottom of the work, a support for said power-operated riveting tool movable upwardly from a low retracted position to carry said riveting tool to a higher operating level with respect to said table and work thereon, means movable with said tool support to move said pilot pin support to retracted position out of the way of said tool support when said pilot pin is retracted, and impositive means for raising and lowering said tool support whereby no damage is done to the machine by jamming of said tool support against said pilot pin support in the event of said pilot pin not being retracted by reason of no rivet being inserted in the work.

33. A riveting machine as set forth in claim 32 wherein the last named means is pneumatically operated.

34. A riveting machine as set forth in claim 32 including motor operated means for turning the riveting tool about a vertical axis during the riveting operation.

35. A riveting machine as set forth in claim 32, including a wedge block above said table guided for movement in transverse relation to said anvil and arranged to have wedging engagement with said anvil when the latter is in engagement with the head of a rivet, whereby positively to prevent upward displacement of the rivet during the riveting operation.

Claims

1. A riveting machine comprising, in combination, an upright frame having a substantially horizontal work table on which work pieces to be riveted together are placed with rivet holes in register, means for feeding rivets one-by-one head up downwardly to the work from above the table with the shank of the rivet in vertically aligned relationship to the rivet holes in the work and through the rivet holes and into a hole provided in said table, the lower end portion of the rivet shank being exposed in said hole provided in the work table so that its projecting portion may be upset against the bottom of the work, the rivet feeding means including anvil means above the table engaging the head of the rivet to prevent its upward displacement during a riveting operation, a riveting tool disposed below said table aligned with the hole therein and the lower end of the rivet shank, a piston vertically disposed in coaxial relationship with the riveting tool, and a pneumatic cylinder in a fixed spaced relation to and below the work table on the frame, said cylinder having said piston reciprocable therein and extending from the upper end thereof and connected with the riveting tool, the cylinder having a source of compressed air connected therewith for reciprocation of said piston during a riveting operation.

2. A riveting machine as set forth in claim l, wherein said cylinder has the source of compressed air connected thereto intermediate the ends thereof, said cylinder having air cushion chambers at the upper and lower ends thereof in the form of closed extensions of its bore of the same diameter as the piston ends in which air is trapped and subjected to compression behind the piston when it projects therein and which by entry of the piston ends therein prevent hammering on either end of said cylinder by said piston.

5. A piston and cylinder assembly as set forth in claim 4, wherein said cylinder also has an air cushion chamber like the other cushion chamber in the upper end thereof for compressing air trapped by the piston when entered partway therein, said cushion chambers preventing hammering by the piston against either end of said cylinder.

6. A piston and cylinder assembly as set forth in claim 5, wherein said assembly by virtue of the air cushion chambers in both ends and the port arrangement establishing communication substantially the same way between the intake port and the other ports and said cushion chambers is operable substantially alike with either end of the cylinder uppermost.

7. In a riveting machine, an upright frame having a substantially horizontal work table carried thereon in which an opening is provided, a pilot pin slidably guided vertically in said opening from below said table, a support for said pin movable laterally relative to the bottom of said table to and from a retracted position but normally held under spring pressure in an operative position with the pin disposed in said opening and projecting upwardly from said table and adapted to have workpieces with rivet holes provided therein stacked by means of their rivet holes on said pin preparatory to being riveted together, said pin being retractable into said support against yieldable resistance means, a riveting tool in aligned relation to said opening and carried on and reciprocable upwardly to said table and downwardly away from it with a part working in a substantially vertical guide carried on said frame below said table, an anvil arranged to engage the head of a rivet from above said table for backup support of said rivet during a riveting operation, a ram carrying said anvil and movable downwardly toward said table and upwardly away from it in aligned relation to said riveting tool and also carrying spring-pressed jaws adapted to carry a rivet with its head end up in front of said anvil so as to engage the pilot pin and force it downwardly out of the rivet holes in the work as the shank of the rivet enters the rivet holes and until the pilot pin is fully retracted below said table, means for feeding rivets one by one between said jaws, means causing opening of the jaws when the rivet enters the rivet holes in the workpieces, means operable in timed relation to the upward movement of said riveting tool to force said pilot pin support with said pin fully retracted therein to a retracted position out of the way of the riveting tool permitting riveting of the workpieces together by upsetting the lower end of the rivet entered in the work, and power means for reciprocating the riveting tool carrying part in a riveting operation.

11. A riveting machine as set forth in claim 7, wherein said pilot pin support comprises a bracket pivoted at one end in a fixed relationship to the underside of said table and having said pilot pin slidably mounted in the other end and normally urged yieldably upwardly relative thereto.

16. A riveting machine as set forth in claim 14, including means positively supporting said anvil against upward displacement by the rivet during the riveting operation by wedging engagement with the upper end of said ram.

17. A riveting machine as set forth in claim 14, including a wedge block slidable in a guide transversely relative to said ram to have wedging engagement with a portion of said ram for positively supporting said anvil against upward displacement by the rivet during the riveting operation, and power operable means for reciprocating said wedge block in timed relation to the reciprocation of said ram to move to operative position after its downstroke and be retracted before its return stroke.

18. A riveting machine as set forth in claim 14, wherein said pilot pin support comprises a bracket pivoted at one end in a fixed relationship to the underside of said tablE and having said pilot pin slidably mounted in the other end and spring-pressed upwardly relative thereto.

22. A riveting machine as set forth in claim 21, wherein the motor has a housing in fixed relation to said cylinder, and its rotor has a rotary spindle driven by and extending from said rotor into said cylinder relative to which said piston is reciprocable, said piston and spindle having a slip connection, whereby rotation is transmitted to said piston during its reciprocation.

25. In combination, a cylinder having a bore therein, a piston reciprocable in said bore and also rotatable, said piston having a rod coaxial and rigid therewith and extending through and closing a central opening provided in one end of said cylinder for connection with a part to be reciprocated and turned simultaneously, said piston having an axial bore provided therein, a motor the housing of which is coaxial and connected with and closes the other end of said cylinder, a rotor rotatable in said motor housing in coaxial relation to said piston, and a drive spindle coaxial with said piston and armature and connected at one end with said armature to have drive transmitted therefrom, said spindle having its other end slidably but nonrotatably connected with said piston in the axial bore thereof to transmit drive thereto from said armature.

26. The combination, as set forth in claim 25, wherein the sliding nonrotary connection is a loose one allowing compressed air to pass freely longitudinally through said piston in moving said piston from a retracted position in said cylinder to an operating zone where said piston is reciprocable.

27. In a riveting machine comprising an upright frame supporting a work table having an opening provided therein, riveting mechanism below said table operable in the opening, anvil mechanism over said table adapted to bear downwardly against the head of a rivet inserted in rivet holes in workpieces placed on said table over said opening, whereby to prevent upward displacement of said rivet during the upsetting of its lower end against the bottom of the work, a pilot pin projecting upwardly relative to said table from said opening prior to the riveting operation for mounting of the workpieces on the table by engagement in the rivet holes from below, and means under said table supporting said pilot pin for retraction therein when a rivet is entered in the rivet holes from above replacing said pin, said pilot pin supporting means being shiftable to an out of the way position with the pin in retracted position to permit operation of said riveting mechanism in said opening.

29. A riveting machine as set forth in claim 27, wherein said pilot pin supporting means comprises an air cylinder with a piston reciprocable up and down therein and carrying said pilot pin thereon, and air supply means communicating with either end of said cylinder whereby said piston is movable upwardly under air pressure to hold said pin in extended operative position or is movable downwardly under air pressure to retract said pin.

31. In a riveting machine, the combination of a worktable on which workpieces to be riveted together are placed with rivet holes in register with an opening provided in said table, rivets being inserted downwardly in the rivet holes head end up, an anvil guided for downward movement in alignment with the opening in said table from above the same for engagement with a rivet head to prevent upward displacement of the rivet during a riveting operation, a power operated riveting tool below said table movable in aligned relation to the anvil and the opening in said table and arranged to upset the projecting lower portion of the rivet upwardly against the bottom of the work, and a wedge block above said table guided for movement in transverse relation to said anvil and arranged to have wedging engagement with said anvil when the latter is in engagement with the head of a rivet, whereby positively to prevent upward displacement of the rivet during the riveting operation.

32. In a riveting machine, the combination of a work table on which workpieces to be riveted together are placed with rivet holes in register with an opening provided in said table, rivets being inserted downwardly in the rivet holes head end up, an anvil guided for downward movement in alignment with the opening in said table from above the same for engagement with a rivet head to prevent upward displacement of the rivet during a riveting operation, a pilot pin carried on and retractable into a support movably mounted under said table for movement to a retracted position relative to said table opening, said pilot pin engaging through the opening in said table in the rivet holes in said workpieces but arranged to be retracted when a rivet entered in the holes in the workpieces comes into engagement with said pilot pin whereby to render said pilot pin support retractable, a power-operated riveting tool below said table in vertical alignment with and arranged to operate through the table opening to upset the projecting lower end portion of a rivet upwardly against the bottom of the work, a support for said power-operated riveting tool movable upwardly from a low retracted position to carry said riveting tool to a higher operating level with respect to said table and work thereon, means movable with said tool support to move said pilot pin support to retracted position out of the way of said tool support when said pilot pin is retracted, and impositive means for raising and lowering said tool support whereby no damage is done to the machine by jamming of said tool support against said pilot pin support in the event of said pilot pin not being retracted by reason of no rivet being inserted in the work.