Abstract:
A holding clamp device, for releasably holding a thick planar article over ground, comprising: an elongated main arm member, defining first and second opposite end portions; a pair of first and second tubular bar members, each defining an outer end portion and an opposite inner end portion; a rail member, integral to an intermediate section of the main arm member and slidably engaged by the second bar member inner end portion, wherein the second bar member is maintained by the rail member parallel to the first bar and wherein the second bar member is movable relative to the first bar member while continuously remaining parallel thereto; a first biasing member, continuously biasing the first and second bar members toward one another; and a second biasing member, for discretely biasing the second bar member away from the first bar member, against the continuous bias of the first biasing member.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a clamp for holding thick planar articles such as thickened plates or the like, and more particularly to a clamp for holding multilayer printed circuit boards in an electroplating acid bath. 
     BACKGROUND OF THE INVENTION 
     It is known in the art of electroplating to use frames on which are removably anchored plates or the like articles to be plated, for holding them while they are being submerged in large acid tanks or baths, e.g. for creating printed circuit boards. 
     In applicant&#39;s U.S. Pat. No. 5,904,820 issued May 18, 1999, there was disclosed and claimed a holding clamp for releasably holding an article to be submerged in a liquid solution bath ahead of a submerged anode bar and to be electroplated therein. This patented holding clamp, destined to downwardly depend from an overlying cathode frame bar, comprises a first and a second elongated arm members made of an electrically conducting material and each defining a lower portion coated with a fluid-tight and electrically insulating sleeve, and an upper and a lower end, the first arm member to be fixedly attached to the cathode frame bar at its upper end, the second arm member being shorter than the first arm member and being pivotally attached to the first arm member and being pivotable between a first limit position in which the lower ends are spaced from one another and a second limit position in which the lower ends abut against one another, the first arm member having electrical current conduction means physically accessible at its lower end. Biasing means biases the arm members lower ends against one another, and a lever member pivotally attached to an intermediate section of the first arm member and located entirely above the first and second arm member sleeves at all times selectively forcibly pivotally biases the second arm member into the first limit position against the action of the biasing means. In this way, the first and second arm members are destined to frictionally hold the article to be electroplated between their lower ends when the second arm member is in its second limit position, thus allowing current to be conducted through the conduction means into the article, with the first and second arm member lower portions destined to be submerged in the solution at the most partially up their sleeves. 
     Such a holding clamp device is very efficient for holding thin single layer planar articles. However, recent technical developments in the printed circuit boards have brought about thicker, multiple layer printed boards. Because of their greater overall thickness, the jaw studs of the prior art holding clamps are much more spread apart than before. Since the relative movement between the two jaws is a pivotal one about a circle of an arc, when the jaws are opened from their closed condition, the jaws do not remain parallel to one another and accordingly, the studs become eventually axially offset relative to one another. This means that electrical conduction between the studs from the two opposite jaws from a given clamp, becomes compromised in a progressively increasing fashion as the jaws are progressively pivoted away from one another. 
     OBJECTS OF THE INVENTION 
     The gist of the present invention is therefore to improve upon applicant&#39;s U.S. Pat. No. 5,904,820, by providing means for relative movement of the pair of jaws from an article holding device, that will constantly maintain the pair of jaws parallel to one another during their relative movement to accommodate therebetween an article of varying thickness to be frictionally taken in sandwich therebetween. 
     A corollary object of the present invention is to address the requirements for holding state of the art printed circuit boards over acid baths. 
     General objects of this invention include: that the holding device be easy and quick to operate; and that the holding device require only one operation for installing or retrieving an article therefrom. 
     SUMMARY OF THE INVENTION 
     In accordance with the objects of the invention, there is disclosed a holding clamp for releasably holding a thickened planar article to be submerged in a liquid solution bath ahead of a submerged anode bar and to be electroplated therein, said holding clamp destined to downwardly depend from an overlying cathode frame bar, said holding clamp comprising: 
     a) an elongated main arm member, made from an electrically conducting material, and defining first and second opposite end portions; 
     b) a pair of first and second tubular bar members, each defining an outer end portion coated with a fluid-tight and electrically insulating sleeve and an opposite inner end portion, each bar member outer end portion having a transverse terminal stud projecting therefrom, said first bar member anchored at its said inner end portion to said main arm member first end portion parallel thereto; 
     c) a rail member, integral to an intermediate section of said main arm member and slidably engaged by said second bar member inner end portion, wherein said second bar member is maintained by said rail member parallel to said first bar and wherein said second bar member is movable relative to said first bar member while continuously remaining parallel thereto, while the pair of said terminal studs remain coaxially aligned; 
     d) a first biasing member, continuously biasing said first and second bar members toward one another; and 
     e) a second biasing member, for discretely biasing said second bar member away from said first bar member, against the continuous bias of said first biasing member. 
     Preferably, said first biasing means includes at least one pair of coil springs, hookingly interconnecting said first and second bar members. Also, said second biasing member could include an arcuate cantilever member defining an engagement leg and an opposite actuation leg, said engagement leg extending between said first and second bar members within their common plane, and a pivotal linkage assembly integral to said main arm member and pivotally mounting an intermediate section of said arcuate cantilever member; wherein upon actuation of said actuation leg to move the latter away from said main arm member, pivotal motion of said cantilever member will bring about frictional engagement of said cantilever member engagement leg against said second bar member for displacement of the latter away from said first bar member. 
     Said cantilever member engagement leg preferably includes a bevelled tip. 
     According to a first embodiment of the invention, there is further provided an elongated handle, operatively mounted to said pivotal linkage assembly for facilitating actuation of said actuation leg. 
     Said second biasing member could then include an arcuate cantilever member defining an engagement leg and an opposite actuation leg, said engagement leg extending between said first and second bar members within their common plane, an elongated elbowed handle member integrally carried by said actuation leg coextensively thereto, and a straight link arm pivotally mounted to an intermediate section of said main arm member and pivotally mounting an intermediate section of said handle member; wherein upon actuation of said handle to move the latter toward said main arm member, there will be brought about frictional engagement of said cantilever member engagement leg against said second bar member for displacement of the latter away from said first bar member. 
     This invention also relates to an alternate embodiment of holding clamp, for releasably holding an article to be submerged in a liquid solution bath ahead of a submerged anode bar and to be electroplated therein, said holding clamp destined to downwardly depend from an overlying cathode frame bar, said holding clamp comprising: 
     a) an elongated main arm member, made from an electrically conducting material, and defining first and second opposite end portions; 
     b) a pair of first and second tubular bar members, each defining an outer end portion coated with a fluid-tight and electrically insulating sleeve and an opposite inner end portion, each bar member outer end portion having a transverse terminal stud projecting therefrom, said first bar member anchored at its said inner end portion to said main arm member first end portion parallel thereto; 
     c) an endless screw member, integral to an intermediate section of said main arm member and to said second bar member inner end portion, said endless screw member maintaining said first and second bar members parallel to each other, and said second bar member being movable relative to said first bar member while continuously remaining parallel thereto, while the pair of said terminal studs remain coaxially aligned; and 
     d) a biasing member, for discretely actuating said endless screw member for biasing said second bar member away from or toward said first bar member. 
     Preferably, said biasing member is an enlarged wheel, carried at a free end portion of said endless screw member, said wheel being manually rotatable by an operator. 
     The invention also extends more generally to a holding clamp device, for releasably holding a thick planar article over ground, comprising: 
     a) an elongated main arm member, defining first and second opposite end portions; 
     b) a pair of first and second tubular bar members, each defining an outer end portion and an opposite inner end portion, 
     c) a rail member, integral to an intermediate section of said main arm member and slidably engaged by said second bar member inner end portion, wherein said second bar member is maintained by said rail member parallel to said first bar and wherein said second bar member is movable relative to said first bar member while continuously remaining parallel thereto 
     d) a first biasing member, continuously biasing said first and second bar members toward one another; and 
     e) a second biasing member, for discretely biasing said second bar member away from said first bar member, against the continuous bias of said first biasing member. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     In the annexed drawings: 
     FIG. 1, is a front elevational sectional view of an acid bath showing an overhanging horizontally supported cathode bar holding a number of downwardly depending holding clamps supporting circuit boards to be electroplated according to a first embodiment of the invention; 
     FIG. 2, is an enlarged perspective view of a first embodiment of holding clamp, with its jaws in closed condition; 
     FIG. 3, is a view similar to FIG. 2, but showing the jaws in their opened condition after pivotal action of the central lever under manual bias from the operator; 
     FIGS. 4 and 5, are plan views of the holding clamp in their conditions of FIGS. 2 and 3, respectively; 
     FIG. 6, is partly broken view at an enlarged scale of the area circumscribed by ellipse  6  of FIG. 5; 
     FIG. 7, is an enlarged view of the area taken within ellipse  7  of FIG.  8 ; 
     FIG. 8, is a cross-sectional view of the closed jaws from FIG. 4; 
     FIG. 9, is an exploded view of the first embodiment of holding clamp from FIGS. 1-8; 
     FIG. 10, is a view similar to FIG. 2 but for a second embodiment of holding clamp, with its jaws again in closed condition; 
     FIG. 11, is a view similar to FIG. 10, but showing the jaws in their opened condition after pivotal action of the central lever under manual bias from the operator; 
     FIGS. 12 and 13, are plan views of the holding clamp in their conditions of FIGS. 10 and 11, respectively; 
     FIG. 14, is an exploded view of the second embodiment of holding clamp from FIGS. 9-13; and 
     FIG. 15, is a plan view of an alternate third embodiment of holding clamp. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1, shows a liquid solution bath or tank  20 , with a top mouth  20   a  and a bottom wall  20   b  and which contains an acid solution  22 . A frame  24  overhangs the top mouth  20   a  of acid tank  20 . Frame  24  comprises a flight bar acting as a negatively charged cathode bar  26 . From cathode bar  26  downwardly depend a number of holding clamps  28  according to a first embodiment of the invention, and illustrated in FIGS. 2 to  9 . Holding clamps  28  are each adapted to hold a thickened planar article  30  to be electroplated, usually of a flat rectangular thick plate as shown in the drawings, through mouth  20   a  and into acid batch  20  but spacedly over the bottom wall  20   b  of the tank  20 . 
     Frame  24  is movable between a lower and an upper limit position, as known in the art. In its upper limit position, the articles  30  clear the mouth  20   a  of the acid bath  20  and the liquid acid volume  22 , while in its lower limit position, the clamps  28  extend through mouth  20   a  and the articles  30  are entirely submerged into the liquid acid volume  22  but spacedly over bottom wall  20   b.    
     When powering means (not shown) are activated, a voltage difference is generated between the cathode element and the anode element, and current is transmitted from the anode element through the acid in the bath, the article, the holding clamp to the cathode bar. This way, the positively charged ions composing the metallic (copper, gold or another suitable metal) anode element are conveyed by the acid solution—being used as a carrier means—and fix themselves to the article  30  outer surface, thus effectively electroplating article  30 . 
     The first embodiment of holding clamp  28  is illustrated in FIGS. 2 to  9 . As best shown in FIGS. 5 and 9, holding clamp includes an elongated clamp arm  32  having at one end a fastening band assembly  33 , for transverse attachment of the horizontal support element (as already discussed in applicant prior U.S. Pat. No 5,904,820, supra, and a pair of integral spaced elongated brackets  34 ,  36 , extending transversely from an intermediate section of clamp arm  32  wherein a short end portion thereof  32   a  remains, and being in spaced register with one another. Each bracket  34 ,  36 , includes on a fraction of its interior planar face  34   a,    36   a,  an inturned groove  34   b,    36   b  in facing register with one another, and an outer free end portion  34   c,    36   c,  opposite main arm  32 . 
     A spacer member  37  (FIG. 9) is mounted between the outer free end portions  34   c,    36   c,  of brackets  34 ,  36 . A first stud support tubular bar  38  is fixedly anchored by bolts  40 ,  40   a,  at one inner end portion thereof  38   a  to the clamp arm end portion  32   a  parallel thereto. A second stud support tubular bar  42  is fixedly anchored by bolts  44 ,  44   a,  at one inner end portion thereof  42   a  to a carriage member  46 . This tubular bar end portion  42   a  is engaged into a complementary open channel section  46   a  made in the carriage member  46 . Carriage member  46  includes a transverse U-shape end tubular slider member  48 , sized for slidable complementary engagement through the mouth formed between the free end portions  34   c,    36   c,  of transverse brackets  34 ,  36 , and into and along the cross-sectionally U-shape grooves  34   b,    36   b  of the clamp arm transverse brackets  34 ,  36 , towards main arm  32 , wherein tubulars bars  38  and  42  remain parallel to one another. Accordingly, as carriage member  46  slides along the rails formed by bracket grooves  34   b,    36   b,  second stud support tubular bar  42  is movable relative to stationary first stud support tubular bar  38 , while both bars  38 ,  42  remain parallel to one another at all times. 
     Each tubular bar  38 ,  42  is as generally described in applicant&#39;s U.S. Pat. No. 5,904,820, supra, and thus further includes (FIG. 8) an outer end portion  38   b,    42   b,  covered by a corrosion-resistant, fluid-tight and electrically insulating protective sheath  50 , opposite inner end portions  38   a,    42   a;  and a cylindroid stud  52 ,  54 , projecting inwardly transversely from the corresponding free end  38   c,    42   c,  of sheathed end portion  38   b,    42   b,  the studs  52 ,  54 , being coaxially aligned. As suggested in FIGS. 2 and 4, biasing means  56  are provided to continuously bias tubular arms  38 ,  42  toward one another, and thus, the free inner ends  52   a,    54   a  of the cylindroid studs  52 ,  54 , coaxially against one another (typically taking a planar board article  30  in sandwich therebetween). Preferably, biasing means  56  preferably includes two pairs of coil springs  58 ,  60 ,  62 ,  64 ; one end  58   a,    60   a,    62   a,    64   a,  of these four coil springs hook around integral ears  66 ,  68 ,  70 ,  72 , transversely projecting from carriage member  46  orthogonally to slider  48 , while the opposite end  58   b,    60   b,    62   b,    64   b  of these four coil springs hook around integral ears  74 ,  76 ,  78 ,  80  projecting transversely from the end portion  32   a  of the clamp main arm  32 . Ears  66 ,  68 , extend in a direction opposite ears  70 ,  72 ; while ears  74 ,  76 , extend in a direction opposite ears  78 ,  80 , wherein, as best illustrated in FIGS. 2 and 3, the coil springs  58 - 64  clear the passageway of the carriage member  46  between the two tubular bars  38 ,  42 . Accordingly, coil springs  58 - 64  continuously biases the opposite pair of otherwise spaced studs  52 ,  54 , to firmly coaxially abut against each other, while the tubular bars  38 ,  42 , remain consequently spaced from one another and parallel to one another. As the tubular bars  38 ,  42 , are forcibly spread apart to put a planar board article  30  in between the studs  52 ,  54 , the coil springs  58 - 64  are stretched (FIG. 3) from their initial released condition (FIG.  2 ). 
     According to the specific features of the present invention, and as clearly shown in FIG. 9, a generally V-shape cantilever member  82  is mounted between the two spaced brackets  34 ,  36 , for relative movement therebetween. Cantilever member  82  includes a bore  82   a  at its intermediate apex, and brackets  34 ,  36 , include a pair of registering bores  34   d,    36   d,  extending through their ungrooved planar faces  34   a,    36   a,  wherein a half-threaded bolt  84  extends through bores  82   a,    34   d,    36   d,  for pivotally interconnecting the cantilever member  82  to the brackets  34 ,  36 . Bores  34   d,    36   d,  are proximate arm  32 , so that cantilever member  82  clear the carriage slider  48  at all times. Cantilever member  82  further includes a first leg  86  having a bevelled tip  86   a,  extending in between stud bars  38 ,  42 , and a second opposite leg  88 , extending away from stud bars  38 ,  42  and diverging from main arm  32 . Cantilever member outer leg  88  is maneuverable to pivot cantilever member inner leg  86  in between the two stud holding bars  38 ,  42 , and to spread apart the latter against the bias of the coil springs  58 - 64 , since the bevelled tip  86   a  of first leg  86  is slidingly frictionally engageable against the smooth external face  46   b  (FIG. 4) of carriage member  46  opposite U-shape channel  46 . 
     To facilitate actuation of cantilever leg  88 , there is provided a manual lever handle bar  90 . Elongated handle bar  90  includes a bored recess  90   a  at its inner end portion, for free engagement by the free end portion of cantilever leg  88  which transversely integrally carries a first innermost finger  92  for pivotal engagement with the opposite bores of the recess  90   a.  In addition, a pair of link rods  94 ,  96 , (FIG. 2) pivotally interconnect a pivot mount  98  at an intermediate section of handle bar  90 , and another pivot mount  100  on a bracket  102  extending transversely inwardly from an intermediate section of the clamp main arm  32  and in general transverse register with pivot mount  98 . Therefore, as the handle bar  90  is pivoted from its released condition illustrated in FIG. 2, away from main arm  32  toward its loaded condition illustrated in FIG. 3, the bevelled end  86   a  of cantilever arm  82  slidingly abuts against carriage member  46  and the latter and associated stud bar  42  is brought into motion away from stud bar  38  against the bias of coil springs  58 - 64 . 
     Preferably, a transverse stopper pin  104  (FIG. 9) is provided to V-cantilever arm  82  intermediate bore  82   a  and pivot mount  92 , to prevent accidental movement of stud bar  42  away from stud bar  38  beyond a set relative distance therebetween, by coming to transversely abut against the link rods  94 ,  96  should the handle bar  90  be pivoted away beyond a set threshold as suggested in FIG. 5 of the drawings. 
     A second embodiment of holding clamp device is shown as  28 ′ in FIGS. 10-14 of the drawings. All corresponding elements with the first embodiment will be primed. In this second embodiment of the invention, the main components remain substantially the same, including the V-shape cantilever arm  82 ′, the carriage member  46 ′, the two pairs of biasing coil springs  58 ′,  60 ′,  62 ′,  64 ′, the main elongated arm  32 ′ and the two sheathed stud supporting bars  38 ′,  42 ′. However, instead of having the maneuvering handle ( 90 , first embodiment) pivoted outward away from arm  32  to spread apart the stud carrying bars ( 38 ,  42 , first embodiment, FIG.  3 ), in the present embodiment, the operating linkage assembly for the cantilever arm  82 ′ is inverted, so that—as illustrated in FIG. 11, it is as the handle bar  90 ′ is pivoted toward main elongated clamp arm  32 ′ that the stud carrying bars  38 ′,  42 ′, become progressively spread apart. 
     More particularly, the improvements brought about are directed at the cantilever arm  82 ′, the transverse brackets  34 ′,  36 ′, and the linkage arm  94 ′. Cantilever member  82 ′ is now integral to and generally coextensive with handle bar  90 ′ by the outer end of its leg  88 ′. Cantilever leg  88 ′ extends in between a pair of ears  110 ,  112 , that transversely depend from the brackets  34 ′,  36 ′,. Ears  110 ,  112 , extend away from stud bars  38 ′,  42 ′, and are bored so as to pivotally receive the pivot finger  92 ′ of cantilever member leg  88 ′. Handle bar  90 ′ includes an intermediate elbowed section  90 ′ a,  and an inner portion  90 ′ b  adjacent cantilever member  82 ′ and comprising an ovoidal slot  114 . Slot  114  is freely engaged by a short thinned section  116   a  of a half-threaded bolt  116 , the opposite end of bolt  116  extending through a registering bore  118  made in the clamp main arm  32 ′. A pin  120  is mounted transversely through thinned bolt section  116   a,  so as to enable free limited sliding motion of bolt section  116  along ovoidal slot  114  of handle bar  90 ′; while a tension spring and nut assembly  122 ,  124 , is mounted to bolt  116  on the side of bar  32 ′ opposite handle  90 ′. 
     In operation, the linkage bolt  116  maintains handle  90 ′ and V-cantilever arm  82 ′ in their released condition, due to the bias of the four large compression springs  58 ′- 64 ′ but against the bias of the single small tension spring  122 . As sequentially suggested in FIGS. 12 and 13, as the handle  90 ′ is pushed toward arm  32 ′, the integral cantilever arm  82 ′ frictionally slides against carriage member  46 ′ thus concurrently displacing carriage member  46 ′ and stud arm  42 ′ away from stationary stud bar  38 ′, against the bias of the coil springs  58 ′- 64 ′ but yielding for a small part to the bias of the bolt spring  122 . 
     A third embodiment of article support device is schematically illustrated as  28 ″ in FIG. 15 of the drawings. Corresponding elements relative to the first embodiment will be double primed. In this third embodiment, the movable stud carrying bar  42 ″ is connected to the stationary stud carrying bar  38 ″, simply by a pair of scisor linkage assemblies  130  (only one scisor linkage is shown in the figure). The five pivotal axes  132 ,  134 ,  136 ,  138 ,  140  of the linkages from the scisor linkage assembly  130  are all orthogonal to the plane extending through both stud carrying bars  38 ″,  42 ″. Relative movement of movable stud carrying bar  42 ″ is controlled simply by an endless screw shaft member  142 , being operatively connected to the scisor linkage assembly intermediate pivot mount  140 . An enlarged rotatable wheel  144  is carried at the outer end of the shaft member  142 , for facilitating rotation of the integral endless screw and therefore relative displacement of movable stud bar  42 ″.