Pneumatic Blind Riveter With Cascaded Pistons

This invention relates to a blind riveter. More particularly this invention concerns a pneumatically powered heavy-duty blind riveter.

A blind riveter (see U.S. Pat. No. 2,396,001) typically comprises a housing provided with a chuck that grips the mandrel of the blind rivet and with means for pulling this chuck back away from an orifice on the housing so as to retract the mandrel in the rivet and thereby upset the rivet end. The chuck is usually of the automatic one-way gripping type and is urged by a spring to a rest position normally adjacent the orifice.

The actuator for this chuck can be pneumatically powered. In order to obtain the necessary force a large-diameter piston is used which is provided with an endpiece that in some pneumatically powered riveters is directly connected with a wedge slidable along rollers. To both sides of this wedge there is provided an arm pivoted on the housing and these arms are connected at the forward section with a transverse rod on which a roller is mounted. The roller lies on the inclined side of the wedge and the front ends of the arms are engaged in recesses in a puller body connected to the chuck. This chuck in the corresponding portion of the housing lies at a right angle to the rest of the housing so that when the actuation wedge is displaced forwardly by the piston the roller engaging the wedge is moved upwardly to lever up the chuck.

The disadvantage of this system is that it is necessary that the relatively complicated actuation device be made to very exact tolerances in order to function properly, thereby making the pneumatic rivet setter a very expensive tool. In addition the device is relatively bulky and hard to use. Therefore the operator tires readily and must often assume an uncomfortable position in order to position the riveter properly over the workpiece.

Another type of device is known which uses a plurality of pneumatic cylinders. The common piston rod for the several pistons is connected directly to the pulling chuck so that the relatively lengthy assembly can be positioned in line with the mandrel at a right angle to the workpiece. Such a position is not only uncomfortable but is often impossible so that such devices have not met with widespread acceptance. In addition the use of several pistons often means that the reset time for the tool is relatively long, as the conventional reset spring is only slowly effective to drive the air out of the compartments in back of all of the pistons.

It is therefore an object of the present invention to provide an improved blind riveter.

Another object is the provision of a pneumatically powered blind riveter that is relative easy to hold and use, and which is of small dimensions.

Another object is to provide a blind riveter which is inexpensive to manufacture.

These objects are attained according to the present invention in a blind riveter wherein the housing is provided with a pneumatic piston whose front end is engageable with the long arm of a two-arm first-class lever whose short arm is operatively engaged with the chuck. In this manner it is possible for the housing to have an easy-to-grip handle containing the pneumatic actuating cylinder and, transverse to this handle, a nose housing the chuck. The lever connection between the actuating mechanism and the chuck therefore form a comfortable-to-hold assembly.

According to another feature of this invention the elongated chamber formed by the housing is subdivided by at least one partition into a plurality of compartments each of which is provided with a respective piston. The pistons are longitudinally aligned and interconnected by a stem. Thus the overall diameter of the housing can be reduced considerably, again making the device much easier to hold, while in no way sacrificing power as the aggregate piston surface area is sufficient, along with the mechanical advantage of the lever, for use of the riveter on virtually any size of rivet.

According to yet another feature of this invention the housing is provided with three such pistons and with a liner formed by three cylindrical tube sections clamped on opposite sides of two partitions. The piston are interconnected by a stem formed of two cylindrical tubes having ends braced against the bases of the pistons and a core rod of noncircular section passing through the two tubes and secured at its two ends via endpieces to the pistons. The two tubes are formed at their extreme front ends with notches and the rear endpiece is formed at its front face with a similar notch so that fluid communication is possible through the passage formed between the noncircular core and the tubes, this passage opening immediately behind each of the pistons. The front compartment is open to the outside air in front of the piston, the middle compartment is open to the outside air through a hole formed in the extreme front end of the compartment, and the rear compartment is connected via a passage to a reversing valve carried on the housing. This reversing valve can feed compressed air either to the space in front of the rear piston so as to pull the three pistons back, or to the space behind the rear piston, thereby also feeding air through the passages to the compartments behind the other two pistons.

In accordance with yet another feature of this invention the control valve is mounted on a collar which is axially and longitudinally nondisplaceable on the housing but rotatable therearound. This control or pilot valve is provided with a longitudinally extending trigger that, when rocked from its normal rest position, can actuate a spool valve so as to operate the riveter. Thus it is possible for the collar carrying the control valve and the trigger on this valve to be arranged at any angle relative to the housing in order that the user may employ that position which is most comfortable for him and not have to worry about the particular position of the feed hose relative to the housing.

According to a further feature of the invention the control valve comprises a reversing spool valve having a spool slidable in a cylinder on the control-valve collar and urged in one direction by a compression spring and displaceable in the opposite direction by compressed air in an end of the cylinder. This compressed air in the end of the cylinder can be released into the atmosphere by rocking of the trigger in order that the spring is effective to displace the valve spool in the opposite direction.

It is also within the scope of the present invention to provide the control valve and trigger rigidly fixed on the housing. In this case the control valve and trigger are secured on the side of the housing corresponding to that side from which the chuck-containing nosepiece projects.

According to a further feature of this invention the long arm of the lever is between one and one-half and three times longer than the short arm invention, preferably twice as long. This lever is of the bell-crank type with its pivot not lying directly between the end of the long arm against which the pistons are effective and the end of the short arm which is connected to the chuck.

The above and other objects, features and advantages of the invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIGS. 1, 2, and 3 are longitudinal sections through the apparatus according to the present invention in unactuated, partially actuated, and fully actuated positions, respectively;

FIG. 4 is a section taken along the line IV--IV of FIG. 3;

FIG. 5 is a large-scale view of a detail of FIG. 3;

FIG. 6 is a longitudinal section through the liner unit of the riveter shown in FIGS. 1-5; and

FIG. 7 is a section taken along line VII--VII of FIG. 6.

As shown in FIGS. 1-3 the riveter according to the present invention has a housing 1 with a cylindrical handle or body part 1A lying on an axis A and a nosepiece 1B lying on an axis A' extending at an angle of approximately 115.degree. to the axis A. This angle has been found particularly comfortable in use. The body 1A of the housing is cylindrical and hollow and provided with a liner formed of three cylindrical tubes 2a, 2b and 2c. Two annular partition disks 3a and 3b, of the same outside diameter as the tubes 2a-c, have O-ring seals 4a and 4b compressed between the tubes 3a and 3b and sections 2a and 2b respectively. The front end of the tube 2a bears against a shoulder 14 at the front end of the housing 1 and the rear engages against a shoulder 21 formed in an end cap 20 that is threaded at 19 to the rear end of the housing body 1A. Diametrically opposite holes 22 are provided in the rear face of this cap 20 for its attachment and removal by means of a pin-type key.

The nosepiece 1B of the housing 1 is provided with a mandrel-gripping chuck 30 of conventional design. The housing part 1B has a closed front wall 25 and an open top. A tension spring 31 is secured between the top end of the puller body 29 and the housing 1 so as to pull this body 29 down into the position shown in FIG. 1.

Three annular and disk pistons 6a, 6b, and 6c provided with respective seals 10a, 10b, and 10c slidable within the tubes 2a, 2b, and 2c. A square-section rod 5 is threaded at both ends and provided at its front end with a hexagonal nut-like endpiece 8 and its rear end with a hexagonal nut-like endpiece 9. This rod 5 passes through all three pistons 6a-c and through two tubes 7a and 7b of circular section. The tube 7a has a front end braced against the rear face of the piston 6a and the rear end recessed in the front face of the piston 6b. The tube 2b has a front end braced against the rear face of the piston 6b and a rear end recessed in the front face of the piston 6c. The tubes 7a and 7b are formed at their front ends with diametrically opposite notches 13a and 13b, respectively, and the front face of the rear end piece 9 is formed with similar notches 13c. In this manner a passage 12 is formed which opens at 13a immediately behind the piston 6a at 13b and immediately behind piston 6b at 13c immediately behind the piston 6b. The chambers 15a, 15b, and 15c are therefore in fluid communication with one another, as best is shown in FIG. 2.

The stem formed by the tubes 7a and 7b and the rod 5 is sealed at the partitions 3a and 3b by O-rings 11a and 11b. The partitions 3a and 3b are formed with respective circumferential grooves 16a and 16b and with backwardly open notches 16a' and 16b', respectively, which place the chambers 55b and 55c in front of the pistons 6b and 6c in communication with these grooves 16b. In addition the housing 1 is formed with a small orifice 17a' at the groove 16a so that the chamber 55b is in communication with the atmosphere. The chamber 55a in front of the piston 6a is in communication with the atmosphere through the open front end of the housing 1.

As shown in FIGS. 6 and 7 this assembly comprising the tube sections 2a-c, partitions 3a and 3b with their associated seals, the pistons 6a-6c with their associated seals and the stem 5-9 can readily be replaced. The tube sections 2a-c are made of steel as is the entire stem 5-9. The pistons 6a -6c, partition walls 3a and 3b are made of a hard synthetic resin, a polyamide such as nylon being very advantageous. The seals 3a-3c and 4a-b are made of a rugged elastomer. This entire assembly can readily be replaced in the housing 1 which is made of aluminum. After much wear, when the pistons 6a-6c begin to leak, it is possible simply to remove the end cap 20 and pull out the entire assembly as shown in FIG. 6, and then replace it with a new assembly. In this manner that part of the tool which wears most rapidly can be replaced so as fully to renew the tool.

The front end of the endpiece 8 bears on a roller 28 carried on a pivot pin 26a extending as shown in FIG. 4 between long arms 27a of two bell crank-type levers 27 of T-shape. A pivot 26 extending through the front part 25 of the housing acts as a fulcrum for the levers 27 which also have short arms 27b between which extends a pin 26b that passes through the puller body 29 at the chuck 30. This puller body 29 is cut out at 32 so that as shown in FIG. 3 the lever 27 can swing into it.

At the back end of the housing there is provided a collar 23 constituting the housing for a control valve 18 provided with a trigger 24 extending parallel to the axis A. This collar housing 23 is rotatable on the housing 1 about the axis A but is prevented from being displaced axially thereon by a shoulder 1' formed on the housing 1 and another shoulder 20' formed on the end cap 20. The housing 1 is formed with a longitudinal groove 17 constituting a passage terminating at one end at the circumferential grooves 16b in the partition 3b and extending all the way to the back end of the housing part 1A. The cap 20 is formed with a pair of radially throughgoing holes 56 and 54 respectively opening at the rear end of the threaded region 19 and at the very rear end of the chamber 15d.

As better shown in FIG. 5 the collar or ring 23 is sealed by O-rings 60 in front of, in back of, and between the holes 56 and 54. In addition the ring 23 is formed with circumferential inwardly open grooves 57 and 53 respectively registering with the holes 56 and 54. This ring 23 is formed with a cylinder 33 subdivided by a spool 34 having O-rings 38 into five longitudinally spaced compartments 48, 35, 36, 37, and 47. Radial holes 58 and 52 extend between the compartments 36 and 37 and the grooves 57 and 53. A compressed air inlet 51 can, depending on the position of valve body 34, open into either chamber 36 or 37. An outlet 59 can also, depending on the position of the valve body 34, open into the compartment 47 or the compartment 37, the compartment 47 always being vented through a small-diameter outlet 49. In addition another vent 49 can open either into the annular compartment 36 or the compartment 35. A passage 50 of very small diameter extends from the compressed-air inlet 51 to the extreme left-hand end of the chamber 48. In addition a compression spring 46 has one end braced against the extreme right-hand end of the cylinder 33 and another end braced against the valve body 34 so as to urge it in a direction that minimizes the volume of chamber 48 and maximizes the volume of chamber 47.

The left-hand end of the cylinders 33 is defined by an annular disk 39 formed with a central opening 42. A ring 40 is screwed into the collar 23 and serves to secure the disk 39 tightly in place. A compression spring 45 is braced between this disk 39 and the handle 24 so as to hold it in a position parallel to the axis A as shown in FIG. 1. The handle 24 has at its rear end an outwardly extending synthetic-resin flange 44 that engages with an inwardly extending lip 41 of the ring 40. When not deflected from the normal position shown in FIG. 1 the handle 24 therefore lies snugly against the ring 40 and prevents air flow out of the chamber 48.

The apparatus functions as follows:

When, as shown in FIG. 1, the handle 24 is parallel to the axis A and compressed air is fed into the inlet 51 there will be a small flow of air through the fine passage 50 into the end chamber 48. As pressure builds up in this chamber 48 the valve body 34 will be pushed to the right as shown in FIG. 3. When all the way into this actuated position the chamber 35 is vented to the atmosphere via opening 49. The compressed air-inlet 51 is connected through passage 36 to hole 58, thence through groove 57 and hole 56 to the passage 17 opening into the chamber 55c in front of the piston 6c. Pressure buildup in the chamber 55c is effective in the direction of arrow P on the piston 6c so as to displace it back until its endpiece 9 comes into contact with the inside of the cap 20. This action fully retracts the pistons 6a-6c and the spring 25 then pulls the lever 27 into the position illustrated in FIG. 1.

In order to set a rivet the mandrel is forced into the self-locking chuck 30, the rivet is inserted into the workpiece, and the handle 24 is actuated as shown in FIG. 2.

Actuation of the handle 24 allows air from the chamber 48 to escape so that the spring 46 pushes the spool 34 to the left as shown in FIGS. 2 and 5. When the spool 31 is all the way to the left the compressed air in the chamber 55c can bleed out through the notches 16b', the groove 16b, the passage 17, and the hole 56, the groove 57, the hole 58, the chamber 36, and the vent hole 49. At the same time air is fed into the chambers 15a-c via the passage 37, the hole 52, the groove 53, the hole 54, and thence passes into the chambers 15a and 15b via the notches 13c, the passage 12, and the notches 13a and 13b. In this manner pressure builds up behind all three of the pistons 6a-6c so it can move them forwardly in the direction of arrows Q. Air in the chamber 55a is forced out through the notches 16a', the groove 16a and the vent hole 17a' and the air in the space 55a in front of the piston 6a simply is forced out through the front of the housing. As the pistons 6a-6c move forward the stem 5-9 similarly moves forward so that endpiece 8 presses on the roller 28 and pivots the levers 27. The mechanical advantage gained by the 2:1 difference in length L and 1 of the arm 27a and 27b is thus effective on the puller body 29 which is forced up against the extensions of springs 31 so as to upset the rivet held in the chuck 30. The pistons 6a-6c move forward until the pistons 6b and 6c virtually rest against the back face of the partitions 3a and 3b, thereby obtaining a relatively long stroke S and exerting considerable force on the rivet via the chuck 30. The cross-sectional size of the passage 50 is very small compared to the cross-sectional size of the outlet or vent opening created by rocking of the lever 24 so that pressure cannot build up in the compartment 48.

After the rivet is set the trigger 24 is allowed to rock back to the position shown in FIG. 1. The chamber 48 is again pressurized through the passage 50 and the spool 34 is moved back to the right against the force of spring 46. When all the way in the right-hand or actuated position the spool 34 again allows air to flow via the passage 17 into the chamber 55c in front of the piston 6c. At the same time air in the chamber 15c, and in the chambers 15a and 15b in fluid communication therewith can bleed out through the radial hole 54, the groove 53, the hole 52, the chamber 37, and the vent hole 59. Thus the spring 31 need not also serve to return the cascaded pistons 6a-c to their starting position.

The device according to the present invention is extremely easy to use and has a very long service life. The user can comfortably grasp the cylindrical body 1B of the housing and actuate the trigger 24 with ease. The hose connected to the inlet orifice 51 can be allowed to run off at any angle, as the collar 23 readily rotates about the housing. It is possible, of course, to provide a screw as illustrated at 61 so as to fix the collar 23 relative to the housing in case it should be desired to maintain it in this single position. The angle of the nosepiece 1A relative to the rest of the housing has also been found extremely comfortable as it allows the user of the tool to press down on the rivet being inserted and to fit it into relatively tight spaces if necessary. Should the tool wear out it is possible to install a new liner unit as shown in FIGS. 6 and 7 in a few minutes so as to fully renew and replace virtually all of those parts of the device which are likely to wear out.