Self-aligning wedge clamp

Abstract: A four directional self-aligning wedge clamp is provided for securing electronic modules (4) in a rack (22). In use, the clamp assembly is slid into a channel (14) of the rack and expanded to engage the walls of the channel. The clamp assembly comprises a number of wedge elements (30,42,44,66,67,78,88) with a central rod (86) passing therethrough. On tightening of the rod (86), wedge elements (66,67) are urged outwards of the clamp assembly against side walls of the channel (14) and further wedge elements (42,44) are urged against the module (4) to provide a substantially rigid assembly.

Description: This invention relates to apparatus for clamping a device to a rack having a longitudinal groove therein, comprising: a rod having a retainer on one end and threads on the other end; a multiplicity of adjacently positioned sections having holes larger in diameter than said rod and receiving said rod therethrough, said sections having complementary sloped faces therebetween; and means for engaging the threads on said rod. Numerous electronic control devices are typically carried aboard airplanes, large ships and in some military vehicles. The usual mounting for such devices is by rack mounting, wherein the individual electronic units are mounted side by side or in a vertical arrangement in an enclosure having means to provide mechanical moorings for the units. Older methods for installing such devices in the rack included the use of flanges mounted on the front face of the individual electronic units which could be bolted to flanges on the rack. Later devices provided clamping apparatus on the rack which captured a flange formed on the front of the individual units to retain the units to the rack. With the establishment of standardized electronic module size specifications has come the need for channel engaging clamps for mechanical retention of the unit or module to the rack. In this type of arrangement, the rack is provided with channels extending into its enclosure on both the top and bottom. In one known apparatus of the kind defined hereinbefore at the beginning and described in a Series 260 "card-Lok" retainer product sheet published by Calmark Corporation, 4915 Walnut Grove Avenue, San Gabriel, California 91776, United States of America, wedge clamps having a series of wedge shaped elements and having a single screw passing therethrough have been utilized to mount printed circuit boards in a rack having a single channel. This form of existing wedge clamp, when relaxed, features a generally aligned series of wedges, each centrally mounted on a single screw and interacting with a wedge shaped element mounted to the printed circuit board to be mounted. The relaxed wedge clamp may be inserted into the channel of the rack when in place, the screw is tightened, causing a shortening of the effective length of the clamp and a consequent transverse displacement of the wedges from their relaxed aligned position. This displacement causes a widening of the effective width of the clamp, thereby creating rigidity with the rack's channels. This type of simple wedge clamp has been considered for use with encased standardized electronic modules and is satisfactory for mounting of low mass units which require a single wedge clamp on opposing sides of the modules but for those modules or units where additional clamps are required due to the increased widths of the units, a stack up of tolerance variations between the channels of the rack and the fixed element of the wedge clamp renders the clamp inoperable. In DE-U 85 29 634 (corresponding to GB-A-2 166 004 and FR-A-25 72 240), there is described an apparatus for mounting a printed circuit board in a groove in a rack. The apparatus includes a rib that is fixed along one edge of one face of the circuit board. The thickness of the circuit board together with the height of the rib just fills the width of the groove. The end faces of the rib are sloped towards each other so that each forms an obtuse exterior angle with the face of the circuit board. A movable wedging portion of the apparatus is provided at each end of the rib and has a complementarily sloped face that engages the adjacent end face of the rib. A screw extends through a longitudinal bore in the rib and engages at each end screw threads in the respective wedging portion. Rotation of the screw causes the movable wedging portions to ride up or down on the end faces of the rib, the bore in the rib allowing movement of the screw towards and away from the circuit card. A leaf spring in the bore is arranged to bias the screw and hence the wedging portions towards the face of the circuit board. A variant of this apparatus is also described in which each of the movable wedging portions is spaced from the adjacent end of the rib by an intermediate movable wedging portion having a channel for the screw. The sloped face of each wedging portion engaged with the screw forms, in this variant, an obtuse exterior angle with the face of the circuit board. Each intermediate wedging portion has sloped end faces that complementarily engage the adjacent sloped faces of the rib and the wedging portion engaged with the screw. The channel in each intermediate wedging portion allows that portion to move transversely of the screw, and a leaf spring is provided to bias the intermediate wedging portion toward the face of the circuit card. When the screw is rotated so as to draw the end wedging portions towards each other, the intermediate wedging portions ride up the sloped faces of the end wedging portions and the rib and away from the face of the circuit card. According to the present invention there is provided apparatus for clamping a device to a rack having a longitudinal groove therein, comprising: a rib on the device having a longitudinal channel therethrough and whose first and second end faces are oppositely sloped to form acute angles relative to the device; a rod having a retainer on one end and threads on the other end; a multiplicity of adjacently positioned sections having holes larger in diameter than said rod and receiving said rod therethrough, said sections having complementary sloped faces therebetween, the sections including two intermediate sections having faces sloped to complementarily engage the first and second end faces of said rib, and two wedge sections having faces sloped to complementarily engage further faces provided on the two intermediate sections; and means for engaging the threads on said rod; the rod being positioned in the longitudinal channel of the rib and extending through the adjacently positioned sections; and the arrangement of the sloped faces being such that, by clamping of the adjacently positioned sections to the rib between the said retainer and the engaging means on engagement of the said threads with the engaging means, the intermediate sections are forced by the end faces of the rib against the device, and each wedge section and the adjacent intermediate section are caused to react against each other transversely in the groove to engage its side walls. A preferred embodiment of the invention takes the form of a wedge clamp for mounting modules to a rack. The rack is provided with elongate channels extending thereinto for receiving edge mounted clamp members of modules to be positioned within the rack. The clamp is designed to provide not only the wedge disalignment clamping transverse to the channel in which the clamp will be fitted, but also to provide clamping in a second direction, that is, axial to the body of the clamped item. When an enclosed module needs to be secured, more than one clamp must be used to provide adequate vibration stability and heat transfer. The simple wedge clamp of the prior art has no provision for realignment to the module and when two or more of the wedge clamps are used side by side, tolerance buildup among the clamps and the channels causes ineffectiveness of the extra clamps. Preferred embodiments of the invention provide an improved edge mounted clamp having displaceable wedges therein; a four directional wedge clamp; a self-aligning wedge clamp; a self-aligning wedge clamp having effective heat transfer capability. In a particular preferred embodiment to be described, an elongate rib is provided upon a module which is to be mounted in the rack. The rib is formed with a passageway therein for receiving a tightening rod. An inclined recess is provided upon each end of the rib, with the greatest magnitude of recess proximal to the body of the module. A pair of linked together bracket members is slidably receivable upon the module body proximate to the rib thereof. Each bracket member is substantially a mirror image of the other, with each having a longitudinally extending wall depending generally perpendicularly from the base thereof. Each bracket member is provided with a protruding region formed thereon which is receivable within one of the recesses of the rib member mounted to the module body, having at the opposing side of said region an angularly formed face which is slidably interactive with one of a pair of first wedge elements. Each first wedge element is substantially a polyhedron having two pairs of parallel faces thereon and a pair of non-parallel faces. One of the pair of non-parallel faces of each first wedge element is engageable with the angularly formed face of a bracket member. A second wedge element is interactive with one of the bracket members through slidable engagement with the wall of the bracket member. The second wedge element engages one of the first wedge elements at the opposing non-parallel face thereof. A third wedge element generally similar in shape to the second wedge element is slidably interactive with the bracket member which is not interactive with the second wedge member. A passageway is provided longitudinally through the protruding regions of each of the bracket members and through the wedge members whereby a passageway is communicative among those elements and the passageway of the rib member. An elongate rod is receivable within the passageways and freely slidable in all thereof except the third wedge element wherein a thread is provided within the passageway which is engageable with threads upon the rod. While in its relaxed state, the apparatus may be freely passed into the channels of the rack. The bracket members are slidably displaceable upon the module to allow self-alignment of adjacent wedge clamps in neighbouring channels of the rack. When the rod is driven into the threads of the second wedge element, the interaction of the wedge elements with each other and the bracket creates an expansion of the apparatus thereby urging it against the sides of the rack channel. In addition, tightening of the threads of the rod effectuates displacement of the bracket in a second direction due to its interaction with the rib member, creating frictional engagement and tightening against the module wall in the second direction. Having become aligned while relaxed, the apparatus becomes stationary on the module when the apparatus is tightened to its expanded state. The invention will now be described by way of example with reference to the accompanying drawings, in which:- Figure 1 is a perspective of an embodiment of the invention mounted to a module. Figure 2 is a front elevation of a rack having a module secured therein by a plurality of embodiments of the invention. Figure 3 is an exploded view in perspective of the preferred embodiment of the invention. Figure 4 is an exploded perspective view of an alternative embodiment of the invention. Referring to the figures, Figure 1 discloses an apparatus 2 embodying the invention and mounted to a standard module 4 on a wall 6 thereof. Apparatus 2 is shown in its relaxed state in this figure. A cutaway portion of a rack 12 discloses channels 14 formed between rails 24. While in its relaxed state, the apparatus 2 may be freely passed into the channels 14 of the rack 12. Figure 2 shows a module 4 mounted at top and bottom sides 6 and 7 respectively to a rack 12. Four of the apparatus 2 are shown mounted to module 4 and each apparatus 2 is received in a channel 14 formed between rails 24 of rack 12. Each apparatus 2 is shown in its expanded state wherein rails 24 are frictionally engaged by apparatus 2 and each apparatus 2 is rigidly fixed upon side 6 or side 7 of module 4. In this Figure, module 4 is sufficiently wide to require two of the apparatuses 2 on each side thereof in order to provide sufficient stability for the mass of module 4 or to provide sufficient heat transfer routing for heat to be exhausted from module 4 to rack 12. Depending upon the mass of module 4 or its heat generation, more or fewer of the apparatuses 2 may be needed to retain module 4 securely to rack 12. The components of the apparatus are disclosed in the exploded view of Figure 3. A rib 30 is mounted to module 4 and engages and interacts with bracket members 42 and 44. A link 60 interconnects bracket members 42 and 44. Bracket member 42 is engaged by a first wedge member 67 and first wedge member 67 engages an engagement wedge 88. The bracket member 44 is engaged by the first wedge member 66 which in turn is engaged by a second wedge 78. First wedge member 66 is generally identical to first wedge member 67 and similarly receives a spring 72 within its passageway 70. A rod 86, which engages a jamming nut 94, interacts with each of the other elements of the apparatus 2 by passing through passageways therein. Referring further to Figure 3, module 4 is depicted in a vertical configuration while rack 12, to which it may engage, is shown partially cut away. Rack 12 is provided with rails 24 along the top wall 22 thereof, the rails 24 defining channels 14 therebetween. In a typical airframe environment, channels 14 are precisely positioned at spaced apart distances and the widths of modules 4 are standardized in incremental widths. In some airframe applications, the width of module 4 is a multiple of 1.5 cm (.6 inch), for example. When module 4 is required to be increased in width, additional securing mechanisms are necessary to adequately secure the module to the rack for vibrational stability or heat transfer. Apparatuses 2 then may be used in multiple, generally parallel configurations, the apparatuses 2 being received in neighbouring channels 14. If clamps were permanently, immovably disposed upon module 4, as is the case with prior art devices, a tolerance buildup among the channels and clamps would result in a reduction of usefulness of the additional clamps; that is, after the first clamp had been set in place, additional clamps would not fit properly in adjacent channels provided. However, the alignment characteristics of the apparatus 2 provide means to utilize the wedge clamps in multiples on the same module. The rib 30 of the apparatus 2 is mounted to module 4 and is provided with a passageway 32 axially therethrough. Rib 30 is provided with opposing ends 34 and 36 which comprise inclined surfaces 38 and 40 respectively which in turn interact with brackets 42 and 44 respectively. The brackets 42 and 44 are mirror images of each other and each includes an elongate base 46 which engages wall 48 of module 4. A ridge 50 depends from base 46 of bracket 44 and is generally perpendicular to base 46. When the apparatus 2 is in its expanded state, base 46 of bracket 44 abuts and is frictionally retained to wall 48 of module 4 by forces exerted by inclined surface 40 of rib 30 interacting with bracket 44. By reference now to bracket 42 only, for clarity purposes, it can be seen that an enlarged region 54 is provided on bracket 42. The enlarged region 54 is provided with a first inclined surface 56 which is appropriately sloped to slidably abut inclined surface 38 of rib 30 when invention 2 is in its relaxed state. Enlarged region 54 also has a second inclined surface 58 positioned diametrically opposing inclined surface 56. The second inclined surface 58 defines a plane which is non-parallel to the plane defined by the first inclined surface 56 of bracket 42. A passageway 76 within enlarged region 54 of bracket 42 communicates with first inclined surface 56 and with second inclined surface 58 and is substantially coaxial with the passageway 32 of rib 30. Since brackets 42 and 44 are mirror images, bracket 44 is provided with identical elements as those of bracket 42, though in reverse configuration. A link 60 flexibly joins brackets 42 and 44, thereby limiting the displacement between end 62 of bracket 42 and end 64 of bracket 44. Link 60 assists in captivation of brackets 42 and 44 to module 4. The wedge members 67 and 66 engage second inclined surfaces 58 and 68 of bracket members 42 and 44 respectively. A passageway 70 passes through wedge member 66 and is provided with retracting spring 72 which affixes to a slot 74 of wedge member 66. The second wedge element 78 is provided with a slant wall 80 which is engageable with an inclined wall 82 of first wedge element 66. A bore 84 is provided through second wedge element 78 and receives a rod 86 which also passes through spring 72 of wedge member 66 and through a passageway of bracket 44 (not in view), through passageway 32 of rib 30 and through passageway 76 of enlarged region 56 of bracket 42. Rod 86 also passes through the spring 72 of other first wedge element 67. The engagement wedge 88 is generally similar to second wedge 78 except that it is provided with a bore 90 with engaging means therein which engages the threads 92 of rod 86. The engagement wedge 88 interacts with first wedge element 67. A jamming nut 94 captures free end 96 of rod 86 to prevent retraction of rod 86 from invention 2 while allowing limited axial movement of rod 86 within the passageways of brackets 42 and 44, rib 30 and first wedge elements 66 and 67 and second wedge element 78 when invention 2 is in its relaxed state. Also, rod 86 is somewhat transversely displaceable within the elements of invention 2 except engagement wedge 88, when invention 2 is in its relaxed state. Selective rotation of rod 86 causes engagement of its threads 92 with the engaging means within bore 90 of engagement wedge 88. When rod 86 is rotated to cause transition from the relaxed state of invention 2 to its expanded state, more of its threads 92 engage with the engaging means of bore 90 of engagement wedge 88. The interaction among brackets 42 and 44, rib 30, first wedge elements 66 and 67, second wedge element 78 and engagement wedge 88 causes the transverse displacement of first wedge elements 66 and 67 relative to the axis of rib 30. The ridges 50 of brackets 42 and 44 are urged against a rail 24 of rack 12 while first wedge elements 66 and 67 are urged against a neighboring rail 24. Also, when rod 86 is driven into engagement wedge 88, brackets 42 and 44 are urged against wall 48 of module 4, thereby fixing the lateral position of brackets 42 and 44 relative to wall 48. An alternative embodiment of the invention is shown in Figure 4. In this embodiment, the invention comprises a series of adjacently positioned elements including a rear wedge 138, a first pair of wedge elements 140 and 164, a second pair of wedge elements 144 and 162, a front wedge 136, and a pair of bracket elements 150 and 152. The bracket elements 150 and 152 are interactive with a rib 130 which is secured to the module 104 which is to be mounted to a rack. The wedge members are interactive with the bracket elements and with each other. A central passageway is formed through the elements in which a rod 166 is receivable. As seen in Figure 4, module 104 is provided with slots 106 and 108 on the face 110 thereof, said face 110 having mounted thereto the rib member 130 by mounting means such as screw 131. Sliding plates 132 and 134 are receivable within slots 106 and 108 and have mounted respectively thereto the front wedge 136 and the rear wedge 138 by screws 139. The front wedge 136 engages first wedge element 140 at first sloped face 142 thereof. The first wedge element 140 engages second wedge element 144 at first sloped face 146 thereof. The first sloped face 146 of second wedge element 144 defines a plane which is non-parallel to that of first sloped face 142 of first wedge element 140. First wedge element 140 is provided with a second sloped face 148 which generally conforms in slope to first sloped face 146 of second wedge element 144. First bracket element 150 and second bracket element 152 are linked by a spring 154. Both first bracket element 150 and second bracket element 152 are slideable on face 110 of module 104 when the invention is not in its expanded state. The second wedge element 144 slidably abuts graduated face 158 of an enlarged region 160 of first bracket element 150 in a manner which will exert forces on second wedge element 144 transverse to the axis of bracket element 150. First bracket element 150 and second bracket element 152 each engage rib 130 and are urged toward face 110 of module 104 when longitudinal forces are exerted on bracket elements 150 and 152 to direct them toward rib 130. Bracket elements 150 and 152 are substantially mirror images of each other. Third wedge element 162 is substantially identical to second wedge element 144 and engages second bracket element 152 in a similar fashion to the manner that second wedge element 144 engages first bracket member 150. Fourth wedge element 164 is substantially a mirror image of first wedge element 140 and operatively engages rear wedge 138 and third wedge element 162 in the same manner as first wedge element 140 engages front wedge 136 and second wedge element 144. The rod 166 is passable through each of front wedge 136, first wedge element 140, second wedge element 144, enlarged region 160 of first bracket element 150, rib 130, enlarged region 161 of second bracket element 152, third wedge element 162 and fourth wedge element 164. Flat washer 172 and lock washer 174 are received upon rod 166. The threads 168 of rod 166 engage threaded opening 169 of rear wedge 138 and are captured at end 170 of rod 166 by jamming nut 172. As torque is applied clockwise to head 167 of rod 166, threads 168 advance in engagement with the threaded hole 169, thereby shortening the effective length of the series of elements and thereby exerting forces to urge bracket elements 150 and 152 toward face 110 of module 104 by the impingement of the end faces 101 and 103 of rib 130 upon the inclined faces 157 and 159 of bracket elements 150 and 152 respectively, and further by the urging of first wedge element 140 upon base 151 of bracket member 150 caused by the force applied by front wedge 136 upon first sloped face 142 of first wedge element 140 and by the urging of fourth wedge element 164 upon base 153 of second bracket member 152 caused by the force applied by rear wedge 138 upon fourth wedge element 164. As rod 166 is driven into rear wedge 138, the clamp moves toward its expanded state wherein wedge elements 144 and 162 are displaced transversely and enlarge the effective width of the invention clamp. In the alternative embodiment of Figure 4, when the invention clamp is in its relaxed state, it is free to move upon module 4 because the passageway 105 of rib 130 is larger in diameter than the diameter of rod 166. Additionally the passageway through the other elements except rear wedge 138 are oversized to allow transverse movement of those elements upon rod 166. As the module 104 is placed in a rack, the invention will align itself with the channel of the rack. After insertion within the channel, rod 166 is driven to engage its threads 168 with threaded hole 169 of rear wedge 138. This compresses the elements, causing wedge elements 162 and 144 to move transversely, thereby expanding the clamp against the rails defining the channels in the rack. Also as compression of the elements is effectuated, bracket elements 150 and 152 are forced against wall 110 of module 104 both by the effect of sloped end faces 101 and 103 and by the forces exerted by front wedge 136 on first sloped face 142 of first wedge element 140 and by rear wedge 138 upon fourth wedge element 164. Sliding plates 132 and 134 self adjust in slots 106 and 108 as rod 166 is rotated. The invention thereby operates to expand in two dimensions, namely transversely within the channel of the rack, and by compression of the invention against the module.

Claims: Apparatus for clamping a device (4) to a rack (12) having a longitudinal groove (14) therein, comprising: a rib (30) on the device (4) having a longitudinal channel (32) therethrough and whose first and second end faces (38,40) are oppositely sloped to form acute angles relative to the device (4); a rod (86) having a retainer on one end and threads (92) on the other end; a multiplicity of adjacently positioned sections (42, 44,66,67,78) having holes larger in diameter than said rod (86) and receiving said rod (86) therethrough, said sections having complementary sloped faces therebetween, the sections including two intermediate sections (42,44) having faces (56) sloped to complementarily engage the first and second end faces (38,40) of said rib (30), and two wedge sections (66,67) having faces (82) sloped to complementarily engage further faces (58,68) provided on the two intermediate sections (42,44); and means (88) for engaging the threads (92) on said rod (86); the rod (86) being positioned in the longitudinal channel (32) of the rib (30) and extending through the adjacently positioned sections (42,44,66,67,78); and the arrangement of the sloped faces being such that, by clamping of the adjacently positioned sections (42,44,66,67,78) to the rib (30) between the said retainer and the engaging means (88) on engagement of the said threads (92) with the engaging means (88), the intermediate sections (42,44) are forced by the end faces (38,40) of the rib (30) against the device (4), and each wedge section (66,67) and the adjacent intermediate section (42,44) are caused to react against each other transversely in the groove (14) to engage its side walls (24). Apparatus according to Claim 1, characterised in that said two intermediate sections (42,44) are flexibly linked. Apparatus according to Claim 1, characterised in that said sloped faces of said two intermediate sections (42,44) engage the faces of said rib (30) in abutment. Apparatus according to Claim 1, characterised in that said two intermediate sections (42,44) are frictionally held to said device (4) when said rod (86) is fully engaged with said engaging means (172).

Inventors: PETERSON KEVIN T, PETERSON, KEVIN T.
Applicants: ROCKWELL INTERNATIONAL CORP, ROCKWELL INTERNATIONAL CORPORATION
Application year: 1991
Main classification: H05K7
IPC codes: H05K7