US2842814A

US2842814A - Clamp

Info

Publication number: US2842814A
Authority: US
Inventors: Erik A Lindgren
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-08-15
Filing date: 1955-08-15
Publication date: 1958-07-15
Anticipated expiration: 1975-07-15

Description

July 15, 1958 E. A. LINDGREN CLAMP 2 Sheets-Sheet 1 Filed Aug. 15?, 1955 INVENTOR y ,1958 EQ A. LINDGREN 2,842,814

CLAMP Y Filed Aug. 15, 1955 2 Sheets-Sheet 2 Z /09 5k fif 7 F r IN 2 EN TOR.

CLAMP Erik A. Lindgren, Chicago, In.

Application August 15, 1955, Serial No. 528,40)

11 Qlaims. (Cl. 20-92) This invention relates to fastening means for the sections of a demountable enclosure and more particularly to a concealed clamp for securing adjacent section frames of a screen room used for electromagnetic and electrostatic shielding in tightly abutting alignment.

It is highly important that the electromagnetic and electrostatic wave shields of the screen room should have their individual screen sections in firm electrical contact along the corresponding marginal edges so that the quality of wave attenuation may be uniform and sustained. This may be accomplished in part by the manner in which the screen sections are secured to the frames. but in addition the fastening means for the frames must be adequate to overcome variations in manufacturing tolerances and to afford easy assembly and disassembly so that the frames and screens will not be damaged. The fastening means currently in use, which utilize nails and screws and the like, do not afford any adjustment in the tightness of fit be tween adjacent frames such as would maintain the contact between respective screen sections despite minor variations in construction, and furthermore such means often occasion damage to the frames, and the effort involved in inserting and removing nails or screws is considerable.

Accordingly, it is an object of the present invention to provide a clamp having separable parts which may be mounted individually on respective sections of a screen room in a predetermined appropriate alignment with the frame ele ents and which permit the frames to be fastened easily and securely in proper relationship.

Another object is to provide a clamp of the type indicated which is adjustable, so that the tightness of the lit between adjacent frame elements may be varied in order to hold the screens in uniform electrical contact despite differences in manufacturing tolerances, and so that only one clamp will be required at each clamping point, with preferably three clamping points vertically spaced at each vertical joint between frame elements.

Another object of the invention is the provision of means for locking adjacent frame members in the desired position after they have been drawn into tightly abutting relation as described.

Another object is to provide release means for disassembly of abutting frame members which requires a minimum of exertion and which entails no damage to the frames themselves.

Other objects and advantages will become apparent as the description proceeds in accordance with the drawings, in which:

Fig. 1 is perspective view of a screen room for electrostatic and electromagnetic wave attenuation embodying the clamp of the present invention;

Fig. 2 is an exploded enlarged perspective view of the clamp according to the invention;

Fig. 3 is a horizontal sectional view of the clamp accordin g to the invention including a fragmentary view of frame elements for the screen room taken along the lines 33 of Fig. l;

nited States Patent ice Fig. 4 is a vertical sectional view of the clamp according to the invention, corresponding to the view shown in Fig. 3 and taken along the lines 44 of Fig. 3;

Fig. 5 is a vertical transverse sectional view, corresponding to the view of section 4 and taken along the line 55 of Fig. 5;

Fig. 6 is an elevational view of a spring button for use with the clamp of the invention, and

Fig. 7 is an exploded perspective view of another embodiment.

Referring now to Fig. 1, the screen room 10 in which the clamp of the present invention is preferably used is of the type shown and described in my copending application No. 338,136, now Patent No. 2,765,362. Individual screen sections 12 of standard size and construction are provided with a shielding screen panel covering each face thereof in electrically isolated relationship, as shown in Fig. 3 at 13, 14, 15 and 16.

The screen should be made of highly conductive metal which possesses adequate tensile strength to withstand outline suspension, preferably 22 mesh copperscreen wire or tinned ferrous wire to secure an effective barrier against emanation or invasion by radio waves within the bands subject to examination. The attenuation in logarithmic units through a shield layer has been evaluated as proportional to the first power of its thickness and to the square root of its conductivity, permeability and the Wave frequency.

The shielding BffiCiIlCY of the screens is related to their conductivity and uonpermeability as wellas to the preservation of continuous electrical conductivity between contiguous parts. By utilizing multiple mutually spaced shielding enclosures formed of appropriate materials, the quality of wave attenuation may be improved and extended over a wide range of frequencies.

The effectiveness of attenuation has also been recognized as factorially dependent upon the establishment of sufficient impedance in respect to'double shield screens and for this purpose each screen of a panel is required to be spaced and electrically insulated from the other. The individual screen panels form inner and outer screen layers each of which completely encompasses the enclosure, and this achievement of conductivity coupling between consecutive sections of the same screen and of isolation between the respective screen shields presents a unique situation, in which the clamp of the invention is especially useful. This is particularly the case where, as is preferred, the screen margins overlie the front edges of the sections as set forth in the aforementioned application No. 308A 36, now Patent No. 2,765,362.

The screen room sections 12 are formed by means .of a frame structure having spaced parallel side members adapted to be secured together along their confronting edges with the adjacent screen panels in electrical contact, the sides being recessed to secure the fastening means of the invention as hereinafter set forth.

Referring now to Figures 2, 4 and 5, a clamp 18 is shown which comprises an elongate rack 26 pivotally secured in a side member 220 f a frame 24 by means of a removable bolt 26 and a detent assembly including a member 238 journal'led on a metal plate Misecured in a side member 32 of a frame 34, a detent finger 36 journalled in the plate 30 having an abutment shoulder 38 integrally formed thereon and a leaf spring 4% secured by a bolt 41 to a transverse flange 43 on plate 30 for biasing the detent finger into locking engagement upon rack 20.

The rack 29 is provided with a contoured or cutout portion 42 adjacent the free end thereof, having a downwardly extending shoulder 44 adapted to 'be engaged by a complementary contoured portion or shoulder '46 of member 28, and teeth 48rare also formed on the rack,

3 along the side opposite cutout portion 42, having a tapered configuration along a forward edge and a substantially vertical shoulder 52 for engagement by detent 36 as will be hereinafter further described.

The side member or upright 22 is provided with an aperture 54 intermediate the edges 56 and 58 covered by screens 13 and 14 respectively and has the rack 20 pivotally secure-d thereto, the rack 20 being disposed in parallel alignment with edges 56 and 58. Aperture 54 is preferably of a height such as to permit the rack 20 to be substantially retracted therein for transportation and storage. In use the rack will be supported on a horizontally extending shelf or ledge perpendicularly to upright 22 and in predetermined relation to member 28 and detent 36 so that detent 36 as urged by spring 40, will ride over the successive tapered edges 50 of the teeth of the rack when the uprights 22 and 32 are moved together with their

frames

24 and 34 in parallel alignment, the rack being adapted to move inwardly at the same time over member 28. A suitable spring (not shown) maybe provided to urge the member counter-clockwise so that shoulder 46 will not obstruct the rack.

The plate 30 is mounted within an aperture 62 in upright 32 by means of a removable bolt 64, the upper and

lower edges

66 and 68 of the plate being preferably set in grooves 70 and 72 in parallel alignment with

edges

74 and 76 covered by screens 15 and 16.

When the

frames

24 and 34 are in coplanar relation apertures 54 and 62 will be offset slightly so that the inward movement of the rack 20 between member 28 and detent 36 will bring the rack '20 into the aperture 62 in relation with plate 30 as shown in Fig. 3, the rack and plate serving as guides to maintain the frames in proper alignment. The rack 20 may also ride upon bolt 64-, as

shown in Fig. 4, to further maintain the parts in a stable relationship.

After the uprights 22 and 32 have been guided into abutting relationship as described, an Allen wrench 78 may be used to clamp them together by inserting an end of the wrench through aperture 77 in upright 32, into a keying recess 80 in the member 28 and rotating the member in a clockwise direction in accordance with the embodiment shown in Fig. 4 so that the shoulder 46 on the member engages the shoulder 44 on contoured portion 42 of the rack to draw the frames into firm engagement along the transverse edges 84 and 86.

When the tightness of fit between the frames has been adjusted as desired, the tension on the rack 20 is maintained by the detent 36, which locks against a shoulder 52 and is held against rotation in the clockwise direction by the bolt 64, which prevents rack 20 from moving downwardly away from the detent in cooperation with the shelf 60. After the frames are thus engaged, a spring button 88 may be used to cover aperture 77 and conceal the mechanism of the clamp, the legs 90 pressing against the walls of the aperture to hold the button securely therem.

In disassembling the screen room 10, the frames may be separated by extracting the bolt 26 so that the rack 20 is in disengaged relation to the upright 22, or by extracting bolt 64 so that the detent 36 no longer holds the rack against outward movement, member 28 being also freely rotatable so as not to oppose withdrawal of the rack.

As seen in Fig. 3, the marginal edges of screens 13, 14, 15 and 16 are drawn inwardly over lands 9.2, 94, 96 and 98 respectively and set downwardly into grooves 163, 102, 104 and 106. The screens are held securely in the grooves by means of inserts, 108, 110, 112 and 114, but it is preferred that the portions of the screens overlying the lands be bowed slightly so as to assure contact between screen sections in the same shielding layer. However, it will be appreciated that uprights 22 and 32, for example, may be slightly out of alignment with one an other, where frames are notperfectly rectangular, and

also that the amount of bowing over the respective lands may vary slightly. Accordingly, it is very desirable to vary the tightness of fit between frames to compensate for such factors, in order that the attenuation quality of the screen room 10 may not be reduced. The clamp of the invention makes it possible to adjust and maintain the tension on rack 20 as desired to accomplish these objectives, and in addition adds greatly to the ease with which the frames can be assembled and disassembled as described.

in Fig. 7, another embodiment of the clamp of the invention is shown wherein a cylinder 116 is provided in place of the member 28, having a radially offset lug 118 formed axially on one end thereof adjacent the peripheral edge 119, the peripheral edge 121 of the other end of the cylinder being toothed. A rack is pivotally secured to upright 22 of the frame 24, as described with respect to rack Ztl, and is provided with a transversely extending slot 122 whose width is preferably slightly more than the diameter of lug 118 and whose length is substantially greater than the diameter of lug 118. The cylinder 116 is adapted to fit relatively snugly in the aperture 77, and the slot 122 is positioned to receive the lug 118 at its lower end when the

frames

24 and 34 are disposed in contiguous parallel relationship. A wrench 124, having a peripherally toothed cylindrical projection 126, is provided to engage with the complementary peripheral edge 121 of cylinder 116, and it is preferred that cylinder 116 have a length substantially less than bore 77 so that the projection 126 of wrench 124 may be held securely in the bore while exerting torque force on the cylinder. When such force is exerted, the cylinder will rotate in position in bore 77, while lug 118 will exert tension force on the rack 120 as it turns. The vertical component of the angular rotation of lug 118 is accommodated by the aforementioned length of slot 122, so that the lug will move from one end of the slot to the other as it is displaced horizontally to move the rack as shown in dot-and-dash in Fig. 7.

Other methods of forming an operative connection between the wrench and the cylinder may be visualized, but it will be appreciated that since the cylinder is journalled in a fixed position in bore 77, the

frames

24 and 34 will be drawn into adjustably snug abutting relationship by rotation of the cylinder as previously described, and this relationship will be maintained by the detent 36.

Although I have described my invention with reference to particular features and advantages thereof, it will be obvious to those skilled in the art that modifications in the details and principles of the invention may be made without departing from the essential concept thereof as set forth in the following claims:

I claim:

1. In a screen room for electric and radio wave attenuation comprising a plurality of screening sections each having a rectangular frame and a metallic screen secured to either side of said frame in electrically spaced relation, a clamp for securing two of said sections together in abutting relation along corresponding side portions of their respective frames for continuous electrical contact between respective screen portions of said frames com prising an elongated rack secured to one of said side portions having a contoured portion formed thereon, a member journalled to the other of said side portions and having a shoulder adapted to engage said contoured portion of said rack when said side portions are moved into contiguous parallel relation and to draw said side portions and said frames into tightly abutting relation when said cam is turned to place said rack under tension force and detent means adapted to engage with said rack to maintain said tension force thereon.

2. The construction according to claim 1 wherein said detent means comprises a detent finger and an abutment shoulder integrally formed therewith, and spring means adapted to exert torque on said abutment shoulder to hold said detent finger in locking engagement with said rack when saidrack is subjected to said clamping tension by said cam.

3. In a screen room for electric and radio wave attenuation comprising a plurality of screening sections each having a rectangular frame and a metallic screen secured to either side of said frame in electrically spaced relation, a clamp for securing side members of said frames together in abutting relationship comprising an elongated rack pivo-tally secured to the outer edge of one of said side members intermediate the edges covered by said screens and parallel therewith, said rack having a contoured portion at the free end thereof, a plate fixedly secured in an aperture formed in the outer edge of the other of said side members intermediate the edges covered by said screen and parallel therewith, a member journalled to said plate and having a shoulder adapted to engage said contoured portion of said rack upon movement of said outer edges of said side members into contiguous parallel relationship and to draw said outer edges and said frames into tightly abutting relationship when said member is turned to place said rack under tension force, and detent means adapted to engage said rack to maintain said tension force thereon.

4. The construction according to claim 3 wherein said detent means comprise a detent finger and an abutment shoulder formed integrally therewith, said finger and shoulder being journalled in said plate in predetermined spaced relation to said member corresponding to the width of said rack-bar, the contoured portion of said rack-bar being formed on one longitudinal edge thereof and the teeth of the rack portion of said rack-bar being formed on the other longitudinal edge of said rack-bar, said detent being adapted to afford entry to said rack therebeneath and over said member when said detent and member are in the inoperative position, and a leaf spring having one end secured to said plate and the other end thereof hearing upon said abutment shoulder whereby to maintain said rack under clamping tension in engagement with said detent.

5. The construction according to claim 4 wherein said first named side portion is apertured to afford upward pivotal movement of said rack and a shelf is formed therein beneath said rack adapted to support said rack in register with the opening defined by said cam and detent.

6. The construction according to claim 3 wherein said rack is pivotally secured to said first-named side portion by removable bolt means whereby to afford suitable disengagement of said clamp.

7. The construction according to claim 6 wherein said plate is secured to said second named side portion by removable bolt means adapted to cooperate with said first named bolt means and affording suitable disengagement of said clamp, said second named bolt means being adapted to oppose pivotal movement of said rack away from said detent when said detent is in locking relationship with said clamp.

8. A fastening element for adjacent sections of a demountable enclosure comprising .an elongated rack mountable on one of said sections said rack including a depending shoulder, a detent assembly mountable on a corresponding edge of the other of said sections and operable to cooperate with said rack to secure the sections in fixed relation, said detent assembly including a spring biased detent finger and a rotatable member having a shoulder adapted to engage said shoulder for locking said sections in tightly abutting relation.

9. In a screen room for radio wave attenuation comprising a plurality of screening sections each having a rectangular frame and a metallic screen secured to either side of said frame in electrically spaced relation and turned inwardly at their marginal edges toward one another along the edges of said frames, a clamp for securing parallel edges of said frames in abutting relation with corresponding inwardly turned marginal edges of said parallel edges in tightly abutting relationship comprising an elongate rack pivotally secured to one of said parallel edges and having a contoured portion at the free end thereof, a detent member journalled in the other of said parallel edges, spring means associated therewith adapted to bring said detent member into locking engagement with said rack when said edges are moved into abutting relation and manually operable rotatable means on said other edge configured to engage said contoured portions of said rack to clamp said edge together.

10. In a screen door for electric and radio wave attenuation comprising a plurality of screening sections each having a rectangular frame and a metallic screen secured to either side of said frame in electrically spaced relation, a clamp for securing two of said sections together in abutting relation along corresponding side portions of their respective frames for continuous electrical contact between respective screen portions of said frames comprising an elongated rack pivotally secured to one of said side portions having a transversely extending slot formed in the free end thereof, a cylinder having a diameter substantially greater than the width of said slot, an axially extending lug on one end of said cylinder offset radially toward the periphery of said cylinder and adapted to be received in said slot, the other of said side portions being cylindrically apertured to receive said cylinder relatively snugly therein when said lug is in said slot, means for exerting torque on said cylinder to place said rack under tension force when said lug is in said slot whereby to draw said side portions and said frames into tightly abutting parallel relation and detent means adapted to engage with said rack to maintain said tension force thereon.

11. In a screen room for electric and radio wave attenuation comprising a plurality of screeing sections each having a rectangular frame and a metallic screen secured to either side of said frame in electrically spaced relation, a clamp for securing two of said sections together in abutting relation along corresponding side portions of their respective frames for continuous electrical contact between respective screen portions of said frames comprising an elongated rack pivotally secured to one of said side portions having a transversely extending slot formed in the free end thereof, a cylinder having a diameter substantially greater than the width of said slot, an axially extending lug on one end of said cylinder offset radially toward the periphery of said cylinder and adapted to be received in said slot, the other end of said cylinder being toothed peripherally, the other of said side portions being cylindrically apertured to receive said cylinder relatively snugly therein when said lug is in said slot, wrench means having a configuration complementary to the toothed configuration of said cylinder for exerting torque on said cylinder to place said rack under tension force when said lug is in said slot whereby to draw said side portions and said frames into tightly abutting parallel relation and detent means adapted to engage with said rack to maintain said tension force thereon.

References Cited in the file of this patent UNITED STATES PATENTS