Solenoid powered riveting tool

Abstract: A solenoid (34,71) actuated blind rivet tool having pulling impulse intensifying means co-acting with the mandrel pulling mechanism (14,20,22,86). One type of impulse intensifying means is a slideable connection of the tool's nose housing (11), housing the assembly for engaging and tensioning the mandrel, and power chamber (36) which comprises the remainder of the tool housing, which power chamber carries a solenoid (34) for powering the tool. The solenoid pulls the nose housing (11) rearwardly until it impacts against the power chamber (55), creating a high-magnitude impulse force to break the mandrel. In lieu of a slideably mounted nosepiece (11), the tool may include a member (86) linked to the pulling mechanism (14,20,22) and a ram (75) which is driven against the member by the solenoid (71) thereby creating an impulse force which is transmitted to the pulling mechanism.

Description: This invention relates to blind rivet tools and more particularly to blind rivet tools having an electromagnetic solenoid for actuating the rivet pulling mechanism. In the field of tools for setting blind rivets, it is conventional to use a pneumatic or hydraulic power source to pull the mandrel of the rivet to set the rivet and break the mandrel stem. An example of such a tool is shown in commonly owned our European Patent Specification EP-A2-130040 US-A-4517820). Attempts have been made to use an electric power source to set a blind rivet. However, these devices require a gear reduction mechanism to obtain sufficient pulling force to break the mandrel stem. An example of such a blind rivet tool is shown in US-A-3095106. Tools of this type have longer rivet setting cycles than the pneumatic or hydraulic type. Another attempt at using an electric power source is shown in US-A-3646791 wherein a stress wave is passed through the rivet to render it momentarily plastic so the rivet can be set. In all of these disclosures, a rivet mandrel is gripped and subjected to a progressive load until the mandrel breaks. DE-U1-86 13 823.5 discloses an electromagnetically-powered blind rivet setting tool comprising rivet engaging members for engaging a rivet mandrel; a sliding element connected to said rivet engaging members for moving said rivet engaging members between advanced and retracted positions; and a solenoid device linked to said sliding element for moving said sliding element and adapted such that upon energizing said solenoid device said sliding element moves said rivet engaging members from the advanced to the retracted position. It is the purpose of the invention to provide an improved blind rivet tool utilising an electromagnetic power source for the pulling mechanism of the tool. According to the present invention, an electromagnetically-powered blind rivet setting tool comprises rivet engaging members for engaging a rivet mandrel; a sliding element connected to said rivet engaging members for moving said rivet engaging members between advanced and retracted positions; a solenoid device linked to said sliding element for moving said sliding element and adapted such that upon energizing said solenoid device said sliding element moves said rivet engaging members from the advanced to the retracted position; wherein a resilient stop is provided with which said sliding element collides when said rivet engaging members reach the retracted position thereby to provide an impulse force, and wherein the mass of said sliding element and rivet engaging members and the pulling force of said solenoid means accelerate said sliding element and rivet engaging members so that upon collision with said resilient stop, the resulting impulse force created breaks the rivet mandrel. Thus the invention utilises a solenoid to operate a rivet engaging and pulling mechanism of a blind rivet tool, with an impulse intensifier creating a large impulse force to break the stem of the mandrel of a blind rivet. It can be seen that the operation of the present invention uses an impulsive shock so as to break the mandrel whereas tools such as that disclosed in DE-U1-86 13 823.5 apply a progressively increasing force to break the mandrel. Even if the mass of the elements of the tool of DE-U1-86 13 823.5 were to be vastly increased and the solenoid pulling force increased, it would not be possible to operate the tool in the manner of the present invention to produce an impulsive shock so as to break the mandrel. In a preferred embodiment, the invention provides a slideable interconnection between a nosepiece for housing the pulling mechanism, and a "power chamber" for housing the remaining tool components including the solenoid. The force induced by the solenoid on the nose housing-pulling mechanism draws these structures toward the solenoid and causes the nose housing and power chamber to collide after the initial operation of the pulling mechanism of the tool. This impact creates an intensified impulse force to break the mandrel stem of a blind rivet. The solenoid pulling force should accelerate and decelerate in a brief enough time, and the moving components should have enough mass, to create a sufficiently large impulse force to break the mandrel. One version of this embodiment fixedly mounts the solenoid coil within the power chamber and the solenoid plunger is drawn rearwardly to draw back the pulling mechanism of the tool. Advantageously, the power chamber includes a sleeve, the nosepiece being mounted to slide on the sleeve in a direction generally axial to the fastener. In a second preferred embodiment of the invention, the solenoid is reciprocably mounted within the tool body. The solenoid, when energised rearwardly, drives a ram until this abuts against a member which is linked to the rivet pulling mechanism, creating an impulse which serves to break the mandrel stem. Advantageously, the action of the solenoid on the ram prior to such impact causes the tensioning of the mandrel stem. For this purpose, a spring other biasing means may be interposed between the ram and the member so that the solenoid force on the ram is transmitted to the member during such period prior to impact. In a variation of the second embodiment, the rivet mandrel gripping and tensioning assembly may be modified, or a different type of rivet may be employed, to reduce or eliminate the need for the rivet mandrel stem for tensioning the mandrel. In order that the invention be better understood, the two preferred embodiments will now be described by way of example in further detail with reference to the accompanying drawings in which: Figure 1 is a sectional view of the blind rivet tool of a first embodiment of this invention, in its rest configuration; Figure 2 is a sectional view of the tool embodiment of Figure 1 showing the position of the nose housing after the solenoid has been energised to draw the pulling mechanism and slideable nose housing to the position at which the impulse force is generated; Figure 3 is a sectional view of a blind rivet tool according to a second embodiment of the invention, in its rest configuration; Figure 4 is a sectional view of the tool of Figure 3, in its jaw tensioning configuration; Figure 5 is a sectional view of the tool of Figure 3, in its impulse force configuration; Figure 6 is a sectional view of the nosepiece portion of an alternative version of the tool of Figures 3-5, in its rest position, shown engaging a double-headed rivet seated in a workpiece; and Figured 7 is a sectional view corresponding to the view of Figure 6, showing the rivet pulling mechanism drawn rearwardly to set the rivet. Reference should be made to Figures 1 and 2 which illustrate a solenoid-powered blind rivet tool in accordance with a first embodiment of the invention. The blind rivet tool 10 of this embodiment contains a nose housing 11 into which a conventional nosepiece 12 is threaded (See Figure 1). Positioned in nose housing 11 is a pair of jaws 14 which are adapted to grip mandrel stem 16 of blind rivet 18 in the conventional manner disclosed in our US-A-3254522. Jaw guide 20 surrounds the jaws 14 and is attached to draw bar 22. Spring 24 is positioned in the draw bar 22 and biases jaw pusher 26 to maintain the jaws 14 open to accept insertion of the mandrel stem 16. When the mandrel stem 16 is inserted into the nosepiece 12 and jaws 14, a rearward force on the draw bar 22 will pull the mandrel stem and set the blind rivet. Threaded into rear 28 of draw bar 22 is front end 30 of core 32 of solenoid 34, these structures being retained in housing 36 of the tool. The tool housing (or power chamber) 36 comprises a rear portion 40 and a forward portion 38 which is secured to rear portion 40 by any convenient means. A conical spring 50 is biased between wall 51 of the forward portion 38 of the housing 36 and a washer 52 positioned on the rear of the draw bar 22. The spring 50 biases the draw bar 22 toward the front of the tool. A sleeve 54 has a flange 55 positioned in end cap 46 and surrounds the draw bar 22. The nose housing 11 has an enlarged rear portion 56 slideably disposed about the sleeve 54. A guide pin 58 in sleeve 54 rides in slot 60 of the nosepiece 11 to maintain the nose housing 11 and sleeve 54 axially aligned. In operation, as the solenoid 34 is energised, the solenoid core 32 will be drawn rearwardly (See Figure 2). This will cause the enlarged rear portion 56 of nose housing 11 to move rearwardly until shoulder 66 abuts flange 55 on sleeve 54. At this instant, the pulling force of the solenoid 34 will be intensified to break the mandrel stem. The magnitude of the impulse force resulting from this abutment increases in proportion to the mass which accelerates and decelerates in conjunction with the rivet gripping and tensioning mechanism, and increases inversely with the square of the time interval over which acceleration and deceleration occurs. Mounted on the rear portion 56 of nose housing 11 is a spring biased pin 68 which is positioned in detent 70 in the sleeve 54. After the rivet is set and the solenoid released, the spring 50 will return the nosepiece 11 to the forward position and the pin 68 will re-engage the detent 70 to eliminate any bounce of the nosepiece on its return to the forward position. It can thus be seen with the sliding interconnection of the sleeve 54 and nosepiece 11, as the shoulder 66 on nosepiece 11 abuts flange 55 on the sleeve 54, the pulling force of solenoid will be momentarily intensified to set the rivet and break the mandrel stem. A second embodiment of the invention is illustrated in the sectional views of Figures 3-5, in which like numerals refer to structures corresponding to those shown in Figures 1 and 2. This second tool incorporates a fixed nosepiece and conventional mandrel pulling mechanism in accordance with US-A-3254522, and utilises a movable solenoid-ram structure to provide an impulse force within the tool in lieu of that provided by the movable nosepiece in the embodiment of Figure 1. This arrangement avoids the disadvantage that movement of the nosepiece away from the workpiece complicates the setting of a rivet therein. Solenoid 71 is slideably mounted with housing 45 the inner wall of which is suitably machined for this purpose. Solenoid 71 is slideably mounted around alloy steel tube 74. Steel tube 74 in turn is slideably mounted around hollow steel rod, which comprises a forward portion 86 threaded into draw bar 22 and a rear portion 87 slideably mounted in rear cap 93 of power chamber 45. A ring 73 of dampening material (such as a foam polymer) and an alloy steel tube 75 (or, in functional terms, "ram") are secured around steel tube 74 at the rear of solenoid 71. Steel tubes 74 and 75 provide high mass and magnetic characteristics suited to the operation of the tool. Solenoid 71 is forwardly biased by outer compression spring 80, while steel tube 74 (with affixed structures 73 and 75) is forwardly biased relative to an elongated member in the form of steel rod by inner compression spring 81 placed between rod 74 and flange portion 89 of rod 85. In the initial, rest position shown in Figure 3, solenoid 71 and tube 74 are in their forward locations due to the action of springs 80 and 81. Upon energising solenoid 71, it presses against pliant ring 73 and steel tube 75, overcoming the respective spring forces to drive tubes 74 and 75 rearwardly until ram 75 impacts against flange 89. During this period, illustrated in Figure 4, the compression of spring 81 exerts a rearward force on flange 89 which produces rearward motion of rod, draw bar 22, and jaw guide 20 while causing jaws 14 to bite into and tension the mandrel stem 16. At the point of impact between ram 75 and flange 89, illustrated in Figure 5, an impulse force is generated and transmitted to the jaws 14 via jaw guide 20 in order to break the mandrel stem 16. Thereafter the solenoid drives compound rod 86, 87 rearwardly until flange 89 rests against dampening material 95 fixed to rear cap 93. Deenergising solenoid 71 permits the return of these mechanisms to their rest configuration of Figure 3. The embodiment of Figures 3-5 shows a colinear, fixed connection between the rod 86, 87 and the pulling mechanisms in nose housing 11, wherein rods 86, 87 act as energy transfer members to transmit the impulse force. Other mechanical linkages may be employed for this purpose. For example, the solenoid and related structures for generating the impulse force could be located in a tool handle at an angle to the nosepiece, and would be coupled to the draw bar by a translation-to-translation linkage. The embodiments of Figures 1-5 have been illustrated using the mandrel pulling mechanism of US-A-3254522 to engage and tension a conventional single-headed rivet 18 (i.e. one having only a rivet-setting head 19). One may also adapt the apparatus of the invention for use with a double-headed rivet, such as that disclosed in our GB-A-2149709. Figures 6 and 7 show in section an alternative nosepiece arrangement for engaging and tensioning a rivet 100 which has a pulling head 105 in addition to the rivet setting head 107. In this embodiment jaw pusher 110 includes a clearance region 111 to accommodate pulling head 105. Rearward motion of the rivet tensioning mechanisms causes jaws 114 to engage and pull back pulling head 105, for setting of the rivet and breaking of the mandrel stem, in accordance with UK patent 2149709. By eliminating the need for gripping of the mandrel by the jaws 114, this embodiment reduces or eliminates the need for tensioning the mandrel stem for gripping purposes in the embodiment of Figures 3-5, and facilitates the breaking of the mandrel stem which would depend essentially on the sudden pulling back on pulling head 105 at the time of generating the impulse force.

Claims: An electromagnetically-powered blind rivet setting tool comprising rivet engaging members (14,20,22) for engaging a rivet mandrel (16); a sliding element (11,86,75) connected to said rivet engaging members for moving said rivet engaging members between advanced and retracted positions; and a solenoid device (34,71) linked to said sliding element (11,86,75) for moving said sliding element and adapted such that upon energizing said solenoid device (34,71) said sliding element (11,86,75) moves said rivet engaging members (14,20,22) from the advanced to the retracted position; characterised in that a resilient stop (54,55,89) is provided with which said sliding element collides when said rivet engaging members reach the retracted position thereby to provide an impulse force and in that the mass of said sliding element (11,86,75) and rivet engaging members (14,20,22) and the pulling force of said solenoid means (34,71) accelerate said sliding element and rivet engaging members so that upon collision with said resilient stop, the resulting impulse force created breaks the rivet mandrel. A blind rivet setting tool according to claim 1 wherein said sliding element (11) comprises a nose housing (11) in which said rivet engaging members (14,20,22) are located; and said resilient stop (54,55) comprises a sleeve (54), on which said nose housing (11) is slideably mounted. A rivet-setting tool according to claim 2 further comprising means for maintaining the sleeve (54) and nose housing (11) in axial alignment. A rivet-setting tool according to claim 2 or 3, further comprising a spring biased pin (68) on said nose housing (11) engageable with a detent (70) on said sleeve (54). A rivet-setting tool according to any one of the preceding claims wherein rivet engaging members include a pair of jaws (14), a jaw guide (20) for causing the jaws to grip the mandrel when said jaw guide is pulled, and a draw bar (22) for pulling the jaw guide, said draw bar being linked to a solenoid core (32). A rivet-setting tool according to any one of the preceding claims wherein the nose housing (11) is mounted to the sleeve (54) so as to slide parallel to the major axis of the rivet. A rivet-setting tool according to any one of the preceding claims wherein said solenoid means (34) is housed in a power chamber (36) located adjacent said sleeve (54). A blind rivet setting tool according to claim 1 wherein said sliding element means comprises a member (85) attached to said rivet engaging members and a ram (75) in sliding engagement with said member (85). A rivet-setting tool according to claim 8 wherein said solenoid means is slideably mounted upon said member (85). A rivet-setting tool according to claims 8 or 9 wherein said resilient stop (89) comprises a flange (89) located upon said member (85) at the end thereof, opposite the end which is attached to said rivet engaging means. A rivet-setting tool according to any one of claims 8 to 10 further comprising a spring (81) interposed between the ram (75) and the resilient stop (89) wherein the driving of the ram towards the member causes the rivet engaging means to tension the rivet mandrel prior to the collision of said ram and said stop. A rivet-setting tool according to any one of the claims 8 to 11 further comprising a housing (45), said solenoid (71) being slideable mounted within said housing to move generally axially to said rivet.

Inventors: WEBER RICHARD G, WEBER, RICHARD G.
Applicants: EMHART INC, EMHART INC.
Application year: 1988
Main classification: B21J15
IPC codes: B21J15