Abstract:
Adapter for increasing the stroke length of a fastener installation tool. The adapter includes a tensile member with a first rack gear, a compressive member with a second rack gear, and a plurality of pinion gears retained within a pinion gear housing. The tensile member is mateable with the puller shaft of the installation tool and with the tensile member of an installation head. The pinion gear housing is mateable with the body of the installation tool. The distal end of the compressive member is mateable with a reducing member, which in turn mates with the outer sleeve of the installation head. Operation of the pulling tool moves the tensile member axially toward the tool body and engages the pinion gears, which in turn move the compressive member axially away from the tool body.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to an adapter assembly for use with a fastener installation tool for installing blind fasteners, and more particularly to an adapter assembly that increases the stroke length provided by an installation tool and to a method for use thereof. 
     BACKGROUND OF THE INVENTION 
     Blind fasteners used in the aerospace and other industries have both a diameter and sleeve length in their respective designs. Some fastener designs are created to produce a large amount of clamp-up, wherein the fastener, when it is installed, pulls the two work pieces together making them as tight as the upset load required to install the fastener. Other fastener designs are created to produce a hole filling requirement, wherein the fastener, when it is installed, expands outward against the work piece hole in which it is positioned, thus having both clamp-up and hole fill characteristics. 
     This second type of fastener is normally referred to as a “wire draw” fastener and comprises an inner, plugging portion attached to the upper stem portion of the fastener and a sleeve portion that is designed to expand when the installation tool pulls the stem portion. During installation, the plugging portion is drawn into the sleeve portion, and the plugging portion is elongated (stretched) within the sleeve portion until the stem is captured within the sleeve portion and breaks away from the plugging portion. 
     Normal fastener installation tools have a stroke length between about 0.45 inches and about 0.75 inches, which can install most blind rivets and many wire draw blind fasteners. However, wire draw blind fasteners are in use now that have longer grips, such as a −06 or a −07 grip length (for extending through a workpiece that is 6/16=⅜ inch or 7/16 inch thick, respectively), and the normal installation tool&#39;s stroke length is insufficient to install the fastener with a single stroke. 
     It is undesirable to use multiple tool strokes to install fasteners, because the first stroke work hardens the fastener. Re-gripping the fastener stem with the installation tool and pulling a second time often causes the stem to break off with too short a length, resulting in an unacceptable installation. Special, long stroke tools must be employed for these wire draw fasteners in the longer grip ranges. However, these special tools are much larger and heavier than standard installation tools, in addition to being much more expensive. 
     Commercial production shops, such as aircraft industry production shops, are replacing air-driven installation tools, attached to air hoses, with cordless, battery-operated installation tools to eliminate the tripping hazard posed by the air hoses dragged along the floor. However, cordless tools do not normally operate as quickly as air-driven tools, requiring two to three times as long to install a fastener. 
     Thus, there is a need for an adapter for use with a standard installation tool that increases the stroke length to allow single-stroke installation of blind fasteners having long grips. There is also a need for an adapter that increases the speed and efficiency of fastener installation in both cordless and standard air-driven tools. 
     SUMMARY OF THE INVENTION 
     To achieve the foregoing and other objects and in accordance with the purpose of the present invention broadly described herein, one embodiment of this invention comprises an adapter for use in installing blind fasteners using an installation tool and an installation head. The installation tool has a puller shaft for applying tensile force and a tool body portion for applying compressive force, and the installation head has a gripping mechanism for applying tensile force to a fastener and a sleeve surrounding the gripping mechanism for applying compressive force. The adapter comprises a tension member having a proximal end mateable with the puller shaft of the installation tool and a distal end mateable with the gripping mechanism of the installation head. The tension member also has a first rack gear formed in its outer surface. The adapter further comprises a compression member having an opening therethrough with an inner surface and is disposed around the tension member. The opening is sized to accommodate relative axial sliding of the tension member relative to the compression member. The compression member has a second rack gear formed in the inner surface. The adapter also comprises a reducing member having a substantially cylindrical opening therethrough, a proximal end mateable with the distal end of the compression member, and a distal end mateable with the installation head sleeve. A pinion gear housing is mateable with the tool body and includes a plurality of pinion gears retained within the housing and engaged with the first and second rack gears. The adapter is operative to increase a stroke length provided by the installation tool. 
     The adapter may be operative to double the stroke length provided by the installation tool or to decrease the time required for installing a fastener. There may be four pinion gears retained within the housing. 
     Another embodiment of the present invention comprises an assembly for installing blind fasteners. The assembly comprises a fastener installation tool having a puller shaft for applying tensile force and a tool body for applying compressive force during operation, a fastener installation head having a gripping mechanism for applying tensile force to a fastener and a sleeve surrounding the gripping mechanism for applying compressive force, and an adapter for joining the tool and the installation head. The adapter comprises a tension member, a compression member, a reducing member, a pinion gear housing, and a plurality of pinion gears retained within the housing. The tension member has a proximal end mateable with the puller shaft of the installation tool, a distal end mateable with the gripping mechanism of the installation head, and a first rack gear formed in its outer surface. The compression member has an opening therethrough and is disposed around the tension member. The compression member has an inner surface with a second rack gear formed in the inner surface. The opening is sized to accommodate relative axial sliding of the tension member relative to the compression member. The reducing member has a substantially cylindrical opening therethrough, a proximal end mateable with the distal end of the compression member and a distal end mateable with the installation head sleeve. The pinion gear housing is mated with the tool body, and the pinion gears are engaged with the first and second rack gears. The adapter is operative to increase a stroke length provided by the installation tool and/or decrease the time required for installing a fastener. 
     The adapter may be operative to double the stroke length provided by the installation tool. Four pinion gears may be retained within the housing. 
     Yet another embodiment of the invention comprises a method for increasing a tool stroke length for installing a blind fastener into a workpiece. The method comprises the steps of providing an installation tool assembly, providing a workpiece having a hole extending therethrough sized to accommodate the blind fastener, inserting the blind fastener through the hole and gripping a stem of the fastener with the gripping mechanism, and using the tool puller shaft to simultaneously apply tensile force to the tensile member of the adapter and compressive force to the pinion gear housing, thereby causing the first rack gear to drive the pinion gears, which in turn drive the second rack gear. The assembly comprises a fastener installation tool having a puller shaft for applying tensile force and a tool body for applying compressive force during operation, a fastener installation head having a gripping mechanism for applying tensile force to a fastener and a sleeve surrounding the gripping mechanism for applying compressive force, and an adapter joining the tool and the installation head. The adapter comprises a tension member, a compression member, a reducing member, and a pinion gear housing that retains a plurality of pinion gears. The tension member has a proximal end mateable with the puller shaft of the installation tool, a distal end mateable with the gripping mechanism of the installation head, and a first rack gear formed in its outer surface. The compression member has an opening therethrough with an inner surface and disposed around the tension member. The opening is sized to accommodate relative axial sliding of the tension member relative to the compression member. The compression member has a second rack gear formed in the inner surface. The reducing member has a substantially cylindrical opening therethrough, a proximal end mated with the distal end of the compression member and a distal end mated with the installation head sleeve. The pinion gear housing is mated with the tool body. The pinion gears are engaged with the first and second rack gears. The tool has a stroke length for relative axial motion between the puller shaft and the tool body, and the adapter is operative to increase the stroke length provided by the installation tool. 
     The using step may comprise installing the fastener using a single tool stroke. The first and second rack gears may have a 1:1 gear ratio, with the using step comprising providing a stroke length to the fastener head that is twice the tool stroke length. The using step may comprise providing a stroke length to the fastener head that is longer than about ⅜ inch and/or decreasing the time required for installing a fastener. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description, appended claims, and accompanying drawings, where: 
         FIG. 1  is a cross sectional view of an adapter of the present invention mounted onto a fastener installation tool; 
         FIG. 2  is a cross sectional view of the adapter of  FIG. 1  with the tensile components retracted axially relative to the compressive components, which have traveled an equal distance in the opposite direction; 
         FIG. 3  is a cross sectional view of a compression member and a side view of a tensile member of the adapter of  FIG. 1  showing rack gears of each member; 
         FIG. 4  is a side view of a pinion gear assembly of the adapter of  FIG. 1 ; 
         FIG. 5  is a distal end view of the pinion gear assembly of  FIG. 4 ; 
         FIG. 6  is a distal end view of the pinion gear assembly of  FIG. 4  with both the outer sleeve rack and puller shaft rack; 
         FIG. 7  is a cross sectional view of an adapter assembly, a fastener, and a work piece prior to installation of a wire draw fastener; and 
         FIG. 8  is a cross sectional view of the adapter assembly of  FIG. 7  after installation of the fastener. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In accordance with the present invention, an adapter may be used to connect a standard installation head to a standard fastener installation tool and provide an increased stroke length for proper installation of blind fasteners that require stroke lengths longer than the normal stroke length of the tool. The adapter provides the installation head with an increased stroke length compared to the installation tool stroke length. In a preferred embodiment, the adapter doubles the tool stroke length. Thus, with the maximum tool stroke length, generally no more than about ¾ inch, the adapter provides an installation head stroke length of up to 1.5 inches. Thus, the adapter can be used to install fasteners requiring stroke lengths of more than ¾ inch in a single stroke, wherein the fastener&#39;s internal drawn portion must be pulled to a length beyond the normal stroke of the fastener installation tool. The adapter can also be used with any standard installation tool and any standard installation head and can be used with conventional fasteners requiring stroke lengths shorter than ¾ inch. 
     As used herein, the term “proximal” refers to a part of a component that is nearest a fastener installation tool. The term “distal” refers to a part of a component that is farthest from the tool. Axial refers to a direction or motion along a central axis passing through the compressive and tensile components of the adapter. 
     As shown in  FIGS. 1 and 2 , adapter  100  comprises a tension member  110 , a compression member  120 , a reducing member  140 , a pinion gear housing  160 , and a plurality of pinion gears  162 . 
     Tension member  110  can be mounted onto an installation tool puller shaft  102 , such as via screw threads  112  at the proximal end of the tension member  110 . Tension member  110  has a series of uniformly spaced rack gear teeth  114  cut into a cylindrical outer surface. As shown in  FIGS. 1-3 , the rack gear teeth  114  are circumferential on the external surface of the tension member  110 , extending all the way around the external surface. Alternatively, the rack teeth could be formed into portions of the circumference. The distal end of tension member  110  is adapted for attachment, such as with screw threads  116 , to a jaw holder assembly  180  of an installation head, shown in  FIGS. 7 and 8 . 
     Compression member  120  comprises a cylindrical sleeve  122  with rack gear teeth  124  cut into its interior surface. Unlike conventional adapters for installation tools, the proximal end  126  of compression member  120  is not directly attached to the compression portion  104  of the installation tool and can move relative to the tool. The proximal end  126  of compression portion member  120  has an inner diameter sized to allow compression member  120  to slide axially relative to the tool. Distal end  128  of compression member  120  is adapted for engagement with reducing member  140 , such as with screw threads  130 . 
     Reducing member  140  is joined to compression member  120 , such as with proximal screw threads  142  that engage distal screw threads  130  of compression member  120 . The outer diameter of reducing member  140  decreases distally, with its distal end  144  joinable to the compression portion of an installation head, such as with external screw threads  146  that are mateable with internal screw threads at the proximal portion of the installation head. The internal surface is preferably cylindrical with an inner diameter selected to position a cylindrical sleeve or compressive portion of a pulling head. Flange  148  extends radially inward, providing additional strength to carry the compression load applied by the installation head sleeve during operation. 
     Referring to  FIGS. 1 ,  2 , and  4 - 6 , a plurality of pinion gears  162  are arranged radially and mounted on high-strength shafts or dowel pins  164  within housing  160 . Pinion gear housing  160  can be joined to the compression member  104  of the installation tool, such as via proximal screw threads  166 . The space between the inner surface of each pinion gear  162  and the outer surface of pin  164  onto which the gear is mounted should allow free rotation of the pinion gear  162  around the pin  164 . A spacing of 0.001 inch has been found satisfactory. For simplicity of construction, it has been found that no additional bearings are required; the pinion gears do not rotate significantly more than one time around the dowel pins  164 . Pinion gears  162  have teeth sized to engage simultaneously external rack gear  114  of tension member  110  and internal rack gear  124  of compression member  120 , allowing rack gear  114  to drive pinion gears  162 , which in turn drive rack gear  124 , compression member  120 , and reducing member  140 . 
     With a normal adapter or with the installation head coupled directly to the installation tool, tensile force is applied via the puller shaft and jaw portion of the installation head, with these parts moving relative to the stationary tool and compressive portion of the installation head. Thus, comparing  FIGS. 1 and 2 , the axial distance D traveled by the puller shaft, jaws, and fastener engaged by the jaws is no more than the maximum travel of the puller shaft relative to the installation tool. 
     Unlike a conventional adapter, the compression member  120  and reducing member  140  do not couple the compression portion of the installation head to the tool body. Thus, the compression member of the adapter and the compression portion of the installation head are not held stationary relative to the tool body, and both the tensile and compression components move relative to the tool body during tool use, such as for fastener installation. Pinion gears  162  cause the compression member  120  to move axially and distally relative to the tool, with the axial motion of the compression member  120  equal and opposite to the axial motion of the tension member  110 . Thus, comparing  FIGS. 1 and 2 , the relative travel distance of the compression and tensile members is 2D, double what one would obtain with a conventional tool and either a conventional adapter or no adapter. The motion of the compression member  120  is transferred to the compression portion of the installation head. 
     As shown in  FIGS. 1-3 , rack gear teeth  114  and  124  and the teeth on pinion gears  162  are sized with a gearing of 1:1, doubling the stroke length of the installation tool. Different gearing may be used to change the factor by which the tool stroke length is changed. The adapter of the present invention may have screw threads or other fastening systems adapted for use with any available installation tool and any available installation head. 
     All parts of the adapter can be formed by machining blocks of a suitable material, such as alloy steel, and then heating the machined blocks for added strength. Alternatively, parts may be cast, followed by grinding the gear teeth into the respective surfaces. For production parts, the rack teeth may be formed into the tension and compression members by turning them on a lathe, such as a CNC machine, and cutting the teeth into the material with a cutting tool. After each tooth is cut, the lathe cutting tool is repositioned to cut the next tooth, moving a distance selected to provide the desired gear tooth pitch, size, and shape. 
     The adapter  100  may be assembled as it is installed onto an installation tool. Pinion gears  162  are secured to pinion gear housing  160  with pins  164 . Compression member  120  is then placed around the pinion gears  162  and pinion gear housing  160 . The rack gear teeth of the sleeve index the pinion gear teeth automatically during assembly. The proximal end of pinion gear housing  160  is screwed or otherwise joined to the compressive portion  104  of the installation tool. Tension member  110  is placed inside compression member  120  by sliding from the distal end of compression member  120 , and tension member  110  is then screwed onto or otherwise joined to the tool puller shaft  102 . The tension member rack teeth ( 114 ) are designed to interface with the pinion gear teeth when the tension member is threaded onto the tool puller shaft ( 102 ). Reducing member  140  is then screwed or otherwise mounted onto the distal end  128  of compression member  120 . The desired installation head is then mounted onto the distal ends of tension member  110  and reducing member  140 . 
     As shown in  FIGS. 7 and 8 , a tool assembly comprising a conventional fastener installation tool, the adapter of the present invention, and a conventional installation head, can be used in a similar manner as a conventional tool assembly to install fasteners. A fastener, such as wire-drawn rivet  170 , is inserted through an opening passing through a work piece  172 , and a lock ring  174  is secured onto the rivet stem  176 . The stem  176  is then inserted through the anvil or nose piece  182  of the installation head compression sleeve  178  and into the distal end of the installation head jaw holder assembly  180 , with the anvil or nose piece  182  of the installation head positioned against the lock ring  174 . As the installation tool is operated, the jaw holder assembly  180  grips the rivet stem  176  and applies tensile force. Simultaneously, pinion gears  162 , engaged with rack teeth  114  and  124 , move compression member  120 , reducing member  140 , and installation head sleeve  178  axially to apply compressive force to rivet sleeve  184 . Rivet plug  186 , attached to rivet stem  176 , is compressed against the distal side of workpiece  172  as rivet stem is pulled axially toward the installation tool. Other types of blind fasteners could be installed with the same installation tool and adapter, with an appropriately selected installation head. 
     Adapter  100  can be used to increase the stroke length for installing fasteners requiring a longer stroke than is provided by conventional installation tools. An additional advantage of the adapter is that it allows standard or conventional fasteners to be installed more quickly with any stroke length. With a tensile member compressive member gearing of 1:1 via pinion gears, and thus a doubled stroke length, a fastener can be installed in one half of the time required with a conventional adapter or with an installation head joined directly to an installation tool. 
     The use of cordless installation tools hitherto provided the advantage of eliminating air hoses and their associated tripping hazard from the installation work area. The present invention adds the ability to use cordless installation tools and achieve the same productivity obtainable with air-driven tools. Indeed, the inventor has used a cordless tool equipped with the adapter to install a variety of blind fasteners in approximately the same time as installation with a conventional air-driven installation tool. Thus, the adapter provides increased efficiency and safety for users, allowing more rapid fastener installation with cordless tools and elimination of the hazards posed by hoses connected to air-driven tools. 
     The foregoing description is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and process shown and described above. Accordingly, all suitable modifications and equivalents may be resorted to falling within the scope of the invention.