US 3181906 A
Description (OCR text may contain errors)
y 1955 I R. A. DE ROSE ETAL 3,181,906
HAND TOOL FOR EXTRACTING PRINTED CIRCUIT CARDS FROM LIBRARY RACKS Filed May 22. 1961 A 7 TOR/Vi Y United States Patent 3,181,906 HAND TOOL FOR EXTRACTING PRINTED CIR- CUlT CARDS FROM LIBRARY RACKS Ralph A. De Rose, Villa Park, and Joseph M. Leo, Evergreen Park, Ill., assignors to International Telephone and Telegraph Corporation, New York, N.Y., a corporation of Maryland Filed May 22, 1961, Ser. No. 111,507 Claims. (Cl. 294-16) This invention relates to hand operated tools and more particularly to extractors for removing printed circuit cards from card library racks.
Modern production methods incorporate so-called printed circuit cards which facilitate modular circuit construction. Briefly, these cards are uniformly shaped sheets of insulating material, such as phenolic resin, for example, having electrically conductive strips deposited thereon to interconnect a number of electrical component terminals. After components are mounted, the cards are fitted into a so-called library rack. In the back of these racks are a number of spring or clip connectors which serve the dual function of electrically and mechanically interconnecting the cards and frame on a plug-in basis. In this manner, defective or obsolescent equipment may be replaced by the simple expedient of unplugging one or more printed circuit cards and plugging in other cards.
A very practical problem is encountered, however, when the printed circuit cards are unplugged and removed from the library rack. As the name library implies, the cards are held in the rack in closely spaced parallel relation much as books are supported on a library bookshelf. This close spacing makes it diflicult to grip and remove the cards. Therefore, various hand tools have been devised for extracting the cards. Strangely enough, the design of these tools has presented many problems since they should not apply any twisting motions which tend to bend or otherwise deform the spring or clip connectors in the back of the rack.
Accordingly, an object of this invention is to provide new and improved hand tools for extracting printed circuit cards from library racks. In this connection, an object is to provide hand tools for extracting these cards from the racks without twisting the rack connectors. More specifically, an object is to apply a hand force through a force multiplying linkage to exert amplified extracting forces on the cards while in position in the rack.
In accordance with one, aspect of this invention, a hand tool for extracting printed circuit cards from library racks includes an elongated base plate having a superstructure mounted on one side and a pair of lift arms dependent from the other side. The length of the base plate is such that it rests against the library rack when the tool is in operating position. The superstructure includes a handle and a force multiplying mechanical linkage connected to extend or retract the arms in response to handle motion. Thus, when the handle is pushed toward the base plate, the linkage retracts the arms toward the base plate. As the arms retract, their ends engage and grip a card to draw it toward the front of the library rack.
embodiment of the invention taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a perspective view showing a library rack including a number of printed circuit cards and a hand tool for extracting the cards;
FIG. 2 is a perspective view of the hand tool with the lift arms extended;
FIG. 2a is a perspective view of the hand tool with the lift arms retracted; and
FIG. 3 is a side view of a latch which may be used for holding the arms in the retracted position.
The principles of the invention are shown in FIG. 1 which includes an exemplary library rack 10 for receiving and supporting a number of printed circuit cards 11. As shown, a hand tool 12 is being used to extract one of the cards 14 from the rack.
The principal portions of the rack 10 are upper and lower support members 15, 16, held in spaced parallel relation by a combination of a terminal board 17 and a pair of brackets 18a, 18b. The support members 15, 16 are separated by a distance a which is slightly less than the length of a side b of the printed circuit card 14. The brackets and support members are transversely grooved to receive the edge of a card, as shown at 20, 21. These grooves provide a series of parallel, vertically aligned, card supporting channels. With this arrangement, the printed circuit cards are held in closely spaced, substantially parallel relation with respect to each other when slipped into the transverse grooves.
By inspection, it is seen that the terminal board 17 is at the rear portion of the library rack and that a number of vertically positioned connectors 22 are aligned with the transverse grooves. These connectors are preferably made in the form of springs or clips positioned to mate with and make electrical contact to conductive strips 23 formed on the far end 24 of the printed circuit card. These connectors must not be twisted or otherwise deformed.
Thus, each card is slid through the grooves until the distant end approaches the terminal board 17. Then the card is pressed into the electrical connectors and circuits are completed between components (not shown) on the cards and frame conductors. For example, bus bars (not shown) running longitudinally along the back of the terminal board 17 may selectively interconnect individual connectors on the terminal board. In addition to completing electrical circuits, the connectors 22 also mechanically grip the printed circuit card 14 to hold it in position.
The problem is to extract the printed circuit card from the library rack. Since the cards are supported in close physical relation, it is diflicult to grip them with a force suflicient to overcome the gripping action of the connectors 22. Moreover, conventional tools allow the cards to twist or otherwise deform the connectors 22.
The principal portions of the hand operated tool 12 are (as best shown in FIG. 2) an elongated base plate 30 having a superstructure 31 on one side and an extractor unit 32 dependent from the other side. The superstructure includes a pair of telescoping posts 33 secured to a handle 35 at one end and to the base plate 30 at the other end. Springs (such as 36) normally bias the handle outwardly and away from the base plate 36. Thus, the handle 35 normally rests in an extended position, as shown in FIG. 2, and may be pushed against spring bias to a lower position, as shown in FIG. 2a. Longitudinally aligned with the telescoping posts and near the ends of the base plate are slots or apertures 37, 38 formed in the base plate to provide guideways for tine like lift arms 46, 41 of the extractor unit. The superstructure also includes a pair of bearing posts 42, 43 mounted on the base plate in longitudinal alignment between the telescoping posts and the apertures 37, 38 in the ends of the base plate.
In carrying out this invention, the superstructure is provided with a force multiplying linkage for interconnecting the handle 35 and the lift arms 40, 41. This force multiplying linkage includes a pair of lever arms 45, 46 terminated at each end in forked configuration. On one end, the fork partially surrounds the telescoping post member; on the other end, the fork partially surrounds the lift arm. At each fork, a pivot pin connects the force multiplying linkage to the post or lift arm, respectively. For example, at the pivot point 47 a pin passing through mating apertures in the ends of the link 45 and the lift arm 40 provide a pivotal connection. Any suitable device such as a retaining spring or C Washer fits into a groove in the pivot pin to hold it in position.
Near, but not at, the center of the lever arms 45, 46, pivot pins connect the lever arms to the bearing posts 42, 43 respectively. The relative lengths of the two ends of these lever arms of the links are selected to multiply the forces applied when the handle 35 is pushed toward the base plate 30 in the direction of the arrow P That is, the lever 50 is longer than the lever 51, thus increasing the forces applied to retract the lift arms.
The extractor unit 32 includes the pair of spaced apart lift arms 40, 41 which have their lower ends bent inwardly (as shown at 52, for example) to form hooks which grip a printed circuit card. The total thickness t of these arms (including the bent end portions) is much less than the length 1 between the transverse grooves in the library rack. Thus, the lift arms may be quickly and easily inserted between printed circuit cards mounted in library racks. To eliminate any danger of short-circuiting, these lift arms are preferably made of non-conductive material, such as nylon.
The length of the arms 40, 41 is fixed by the shapes and dimensions of the cards. More specifically, the far end of the cards (i.e. the end at the back of the library rack) that carries the conductive strips 23 and makes the electrical contact with the frame connectors 22 has notched corners (as shown at c, FIG. 1). The vertical edge of these notched corners form abutments for receiving the lower ends of the arms. Thus, when the arms 40, 41 are slipped between the cards, the hooks (such as 52) fit over over the abutments and apply gripping forces to the card. The dimensions of the cards and of the lift arms, linkage. and other superstructure are selected so that the hooks move inwardly toward the base plate 30 by a distance d (FIG. 1) through which the cards travel when pressed into the frame connectors 22.
The length of the base plate 30 exceeds the distance a so that the ends of the base plate rest against the upper and lower supporting members 15, 16 when the tool is held perpendicularly to the members.
To remove a printed circuit card, the handle 35 is pushed in the direction of arrow P while the members 15, 16 in effect push in the directions of arrows P and P Since the arms 40, 41 are spaced apart to grip the corners, the forces indicated by these arrows are distributed over the width of the card. In this manner, a steady evenly applied force slides the card out of contact with the connectors 22 without any twisting which might tend to bend or otherwise deform the connectors. When the handle reaches its lowermost position, the card is completely free of the connectors and securely gripped between the base plate and the extractor arm hooks. The lower side of the base plate may be grooved to receive the front edge of the printed circuit card, thereby reducing any tendency to deform the card.
A latch means may be used to hold the handle in its lowermost position to maintain the grip on the printed circuit card. This latch means (FIG. 3) includes a pushbutton 60 which slides through the handle 35 and pivotally connects to a latch bar 61 at point 62. The latch bar 61 is pivotally secured to the handle 35 via a bearing post 63. The lower end of the latch bar is inclined at the heavily inked edge 64 to guide it through an opening e in the base plate. Thereafter, the latch bar hooks over the base plate under the bias of spring 65. To release the grip on the card, the pushbutton may be pushed to release the latch so that the telescoping post bias springs (such as 36) push the handle 35 to its uppermost position (as shown in the top half of FIG. 2) thus releasing the printed circuit card.
Replacing cards in the rack is not a serious problem which requires any attention. The cards are fitted into the transverse grooves and gently slid into position by hand. The hand will feel any binding and allow the card to be repositioned before the connectors 22 are damaged. Any attempt to force the cards into position by a tool loses the sense of touch required to complete this operation and may result in connector damage.
It is to be understood that the foregoing description of a specific embodiment of the invention is not to be construed as a limitation upon its scope.
1. An extractor tool for removing printed circuit cards from card library racks comprising base plate means, handle means mounted on one side of said base plate, extractor means extending from the opposite side of said base plate, said extractor means having hook means at the end furthest from said handle, force multiplying linkage means operated responsive to an actuation of said handle means toward said base for moving said extractor means in a direction opposite the direction of motion of said handle to shorten the distance from said hook means to said base plate means.
2. The extractor tool of claim 1 including latch means for locking said extractor means in the position of said shortened distance.
3. A hand tool for extracting printed circuit cards from card library racks comprising a base plate, spring biased telescoping post means mounted on one side of said base, handle means connected to said post means for moving said posts into a telescoped position against the force of said spring bias, a pair of slots extending through said base plate from said one side to the opposite side, a pair of parallel spaced apart tine-like hook terminated lift arms extending through said slots projecting a certain distance from said opposite side, and force multiplying link means operably connecting said lift arms to said telescoping post means to retract said lift arms and shorten said certain distance responsive to the movement of said posts into said telescoped position and to extend said arms said certain distance responsive to the movement of said posts into said non-telescoped position.
4. The hand tool of claim 3 including latch means for holding said lift arms retracted and means for selectively releasing said latch means.
5. The hand tool of claim 4 wherein said force multiplying means comprises lever arm means movably connected at one extremity to said lift arms and at the other extremity to said telescoping post means and bearing post means permanently affixed to said base plate and providing a fulcrum bearing surface at a point on said lever arm means closer to said lift arm means than to said telescoping post means.
6. An extractor comprising a base plate having a superstructure mounted on one side thereof and an extractor unit dependent from the opposite side, said superstructure including a spring biased handle, said unit including a pair of tine-like lift arms, said arms shaped to fit between cards which are mounted in a library rack, guideway means in said base plate limiting said arms to reciprocating motion, means interconnecting said handle and lift arms for retracting said arms in response to actuation of said handle against the force of said spring, and hook means at the extremity of said lift arms whereby said arms are used for engaging and gripping printed circuit cards when said handle is actuated to retract said arms.
7. A hand tool comprising a base plate having a superstructure mounted on one side thereof and an extractor unit dependent from the opposite side, said superstructure including a handle mounted on one end of spring biased telescoping posts, the other end of said posts being connected to said base plate, said unit including a pair of tine-like lift arms shaped to fit between cards mounted in printed circuit card library racks, means interconnecting said posts and arms for concurrent movement, guideway means in said base plate limiting said arms to reciprocal motion, and hook means at the extremity of said lift arms for engagedly gripping a printed circuit card in response to actuation of said handle toward said base plate against the bias of said spring.
8. The extractor of claim 6 and latch means interconnecting said handle and said base plate for maintaining said grip on a printed circuit card, and means for selectively releasing said latch to free a printed circuit card from said extractor.
9. The extractor of claim 6 wherein said means for retracting said arms comprises a force multiplying linkage interconnecting said handle and said lift arms.
10. The hand tool of claim 7 and latch means for main- U? taining said grip on a printed circuit card, and means for selectively releasing said latch to free a printed circuit card from said extractor.
References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Yevchak et al.: I.B.M. Technical Disclosure Bulletin, October 1959, page 38.
SAMUEL F. COLEMAN, Primary Examiner.
JOSEPH D. SEERS, ERNEST A. FALLER, 111.,