US3345025A

US3345025A - Tube lift mechanism

Info

Publication number: US3345025A
Application number: US501938A
Authority: US
Inventors: Robert W Shawfrank
Original assignee: SHAWFRANK ENGINEERING CORP
Current assignee: SHAWFRANK ENGINEERING Corp
Priority date: 1965-10-22
Filing date: 1965-10-22
Publication date: 1967-10-03
Anticipated expiration: 1984-10-03

Description

Oct. 3, 1967 R. w. SHAWFRANK TUBE LIFT MECHANISM 2 Sheets-Sheet 1 Filed Oct. 22, 1965 Inventor- Robert W.5hawrc\nk .fi'll'or'ne ls Oct. 3, 1967 R. w. SHAWFRANK TUBE LIFT MECHANISM 2 SheetsSheet 2 Filed Oct. 22, 1965 Inv encor- Robert W. Shawfrank.

' fitter-megs United States Patent 3,345,025 TUBE LIFT MECHANISM Robert W. Shawfrank, Des Plaines, Ill., assignor to The Shawfrank Engineering Corporation, Des Plaines, Ill., a corporation of Illinois Filed Oct. 22, 1965, Ser. No. 501,938 5 Claims. (Cl. 248123) ABSTRACT OF THE DISCLOSURE A tube lift mechanism for supporting and vertically locating a cathode ray tube or similar article on a portable exhaust cart during fabrication of such article. The lift mechanism is effectively counterbalanced at all set positions to provide smoothness of operation and accuracy of positioning and incorporates a pair of vertical support columns telescopically received Within associated sleeve guides which, because of the interfit therebetween, permits the accommodation of cathode ray tubes or other objects of differing weights with a predetermined weight range without adjustment.

This invention relates in general to portable exhaust carts of the type suitable for use in the fabrication of cathode ray tubes and more particularly to an improved tube lift mechanism for such exhaust carts for vertically locating cathode ray tubes of varying size and weights thereon with smoothness and accuracy prior to drawing a vacuum and sealing ofl? the tubular portion of the tube.

In the manufacture of cathode ray tubes, either monochrome or color, the tube envelope is usually fabricated first and the gun structure is subsequently joined to the envelope. The tube is then exhausted and the tubulature sealed off at the neck portion to provide an evacuated and operational tube. The usual practice is to provide a hollow glass pipe extension, commonly referred to as the exhaust tubulature, at the base of the neck, thru which the tube envelope may be conveniently evacuated. Upon reaching the proper degree of evacuation, the tubulature is heated in a sealing area and collapses inwardly in that area to seal off the tube.

Prior to sealing, the cathode ray tube must be baked in an oven chamber to drive out gases from the aquadag coating, the gun assemblies, and other internal parts. A separate heating device, commonly referred to as a tipotf oven, is employed to apply the required heat locally to the exhaust tubulature to effect sealing of the same at the proper time. During the fabrication operation, the baking operation, and particularly during the time the exhaust tubulature is being sealed off, the cathode ray tube must be carefully supported. In addition, the cathode ray tube must be vertically located or positioned on the exhaust cart so that the exhaust tubulature engages and disengages the exhausting system and tip-off oven structure. This requires particularly delicate positioning because of the fragile nature of the exhaust tubulature (being formed of relatively thin-walled glass) and alignment requirements of the tube pins. The tube lift mechanism therefore must exhibit smoothness of movement as well as permit accurate control over very small increments of vertical movement for alignment purposes. In addition, it is desirable that the lift mechanism :be capable of accommodating different types of cathode ray tubes having differing weights, within a predetermined range, without requiring individual adjustments for each weight.

Heretofore, the vertical positioning of the cathode ray tubes on such exhaust carts has been commonly achieved by tube lifts with rack and pinion gear arrangements or negator springs coupled between the support structure for the tube and the cart frame. These prior arrangements,

3,345.25 Patented Oct. 3, 1967 however, have proved less than satisfactory. This has been principally because of the inability of these devices to provide movements of sufiiciently small increments and smoothness of movement for the cathode and to accommodate cathode ray tubes without requiring individual adjustments.

In accordance with a preferred embodiment of the present invention, a tube lift mechanism is provided for Ea portable exhaust cart wherein a tube support frame or yoke seats on the bell portion of the cathode ray tube and in turn is supported by a pair of vertical support columns. These columns are telescopically received within associated sleeve guides anchored to the cart frame. The columns themselves are supported by a pair of lever members pivotally supported from the cart frame at approximately their centers. Each lever includes a stop, such as a circular cam or roller, at one end to engage a face formed at the bottom of the vertical support column. A counter weight is positioned at the other ends of the lever member so as to be supported therebetween. The counterweight thus moving downwardly as the supported tube is moved upwardly, and vice versa. In one embodiment of the present invention, the counterweight is pendulously supported from a pivot point near one end on each of the lever members and hangs vertically therefrom at all set positions of the lever members rather than rotating in unison with them. In still another embodiment, the aforementioned counterweight structure utilizes a cylindrical member with a hollow core into which may be inserted additional selected weights in the form of a solid rod. The inner insertable rod Weights rolling within the hollow outer weight under the influence of gravity to again maintain the center of gravity of the counterweight structure in vertical alignment with the pivot point on the end of the levers. The sleeve guides are constructed to have a friction-fit on the slidable vertical support columns and provide sufficient frictional resistance to movement to hold the lifting mechanism unit in any one of the Various set positions. It has been found that this balancing action takes place even with substantial variations in tube Weight. iIn addition, unusual smoothness of movement for the ;lift mechanism as a whole is achieved,- permitting the operator to impart very small increments of vertical movement of the cathode ray tubes supported on the exhaust cart.

Accordingly, it is an object of the present invention to provide an improved cathode ray tube lifting mechanism for an exhaust cart which is capable of small increments of vertical movement and characterized by smoothness and accuracy of such movement.

Another object of the present invention is to provide an apparatus of the above type that accommodates cathode ray tubes of diifering weights.

A more particular object of the present invention is to provide an exhaust cart with an improved tube lift mechanism of the foregoing type wherein lever means, pivotably supported intermediate their respective ends, pendulously support a counterweight at one end thereof and a slidable vertical support column at each of the other of the respective ends between which a cathode ray tube or smilar article may be supported and moved between predetermined limits of vertical travel.

Still another object of the present invention is to provide an improved tube lift mechanism for an exhaust cart of the foregoing type wherein vertical columns supporting the cathode ray tube interfit with associated sleeve guides in a manner effective to hold the tube or similar article within a given range of weights in any selected vertical position.

Still another object of the present invention is to provide an exhaust cart for cathode ray tubes with an improved tube lift mechanism wherein the counterweight 3 has a hollow core adapted to receive selected weights therein so as to extend the range of the tube weights that can be accommodated.

It is a further object of the present invention to provide an exhaust cart for cathode ray tubes with an improved tube lift mechanism utilizing features of construction, combination, and arrangement wherein a simple, effective and readily manufactured structure is provided, to the end that a product of maximum commercial usefulness is achieved.

The novel features which are believed to be characteristic of the present invention are set forth with particularity in the appended claims. The invention, itself, however, together with further objects and advantages thereof, will best be understood by reference to the following description taken in conjunction with the drawings, in which:

FIGURE 1 is a perspective view of an exhaust cart having a tube lift mechanism constructed in accordance with the present invention;

FIGURE 2 is an enlarged fragmentary view in crosssection showing the exhaust chuck and tip-off oven assemblies;

FIGURE 3 is an enlarged fragmentary view of the exhaust tubulature and neck portion of a cathode ray tube;

FIGURE 4 is a fragmentary elevation view from the side showing the tube lift mechanism in the fully lowered position;

FIGURE 5 is a fragmentary elevation view from the side showing the tube lift mechanism in the fully upraised position;

FIGURE 6 is an enlarged fragmentary view in crosssection of a sleeve guide and associated support column;

FIGURE 7 is a fragmentary view in perspective of a counterweight with a hollow core;

FIGURE 8 is a diagrammatic representation of a portion of the lever and counterweight in different set positions; and

FIGURE 9 is a view from the side in partial cross section showing the hollow core counterweight and additional weight inserted therein.

Referring now to the drawings, an exhaust cart 10 is shown in FIGURE 1 constructed in accordance with a preferred embodiment of the present invention. The cart 10 includes a four-legged frame 11 having a bottom tray 12 and a top or table 13 and a caster 14 under each of the legs. The underside of the cart table 13 provides a convenient space to accommodate the necessary electrical control equipment such as fuses, terminal boards, relays and the like, such associated equipment not being shown in detail as it forms no part of the present invention. A vacuum pump 15 may be mounted in the bottom of the tray 12 and controlled by any suitable means, such as an electric motor 16 which may be mounted adjacent thereto in the manner shown.

The cart 10 further includes a pair of inverted T-shaped sleeve guides 20 (FIGURES 4, 5 and 6), which guides include a flange portion 20a and a tubular portion 20b extending perpendicularly therefrom. The top or forward end of the tubular portion 20b includes a shoulder 20s followed by a threaded section 2th (best shown in FIG- URE 6). The flange portion 20a is adapted to be atfixed to the cart, such as to the underside of the table 13. The flange portion 20a is secured thereby by mounting bolts 21 with the tubular portion 20b of the respective guides 20 extending upwardly thru clearance holes in the table 13. Each of the sleeve guides 20 is adapted to slidably receive an associated support column 21 therein and maintain the same in vertical alignment. Each of the columns 21 includes a U-shaped flange or support yoke 23 (FIG- URE 1) at the top end with the arms facing inwardly in the manner shown. The support yokes 23 are adapted to support a cathode ray tube 24 therebetween with tips or arms of the yokes bearing against the bell portion of the tube 24.

The cart 10 further includes an exhaust chuck assembly 4 (best seen in FIGURE 2), a tip-off oven assembly 32 and an R-F coil assembly 34, the function of which will be sub equently explained. The R-F coil assembly 34 consists of a rectangular base plate 34a of a length to overlay the tops of the sleeve guides 20 (FIGURE 1). Suitable clearance holes may be provided in the base plate 34a so as to receive the forward threaded portion 20t of the sleeve guides 20 therethrough and rest on the shoulder portion 20s as shown in FIGURE 6. A mounting nut 35 is threaded on the sleeve 20 to hold the mounting plate 34a and in turn maintain the oven assembly 34 securely in the position as shown in FIGURE 1, the R-F coil assembly 34 includes a centrally located opening 340 through which the neck portion 2411 of the tube 24 may extend (FIGURES l and 2).

The tip-off oven assembly 32 includes a disc 32a constructed of a suitable thermal absorbant material, such as ceramic, which has a plurality of heater wires embedded therein (not shown). The heater wires are supplied electrical power through the pair of supply terminals 32t located on the side of the disc 32a (FIGURE 2). The disc 32a further includes a central opening 32b through which the tubulature 24! may pass. A plurality of pin receptacles ring the periphery of the disc opening 32a for receiving the various tube pins of the cathode ray tube 24. The pin receptacles enable the base of the tube 24 to be securely held in an immobilized position throughout the various steps and operations performed on the tube 24 as described below.

The disc 32a is mounted on a horizontal support arm 32c and, in turn, the arm 320 is mounted on a vertical shaft 32s. The shaft 32a is hollow so as to permit electrical contors 32 w to pass therethrough and supply the necessary electrical power to the disc 32a. The shaft 32s is maintained in vertical alignment by a sleeve guide 36 affixed to the underside of the table 13 as shown. A U-shaped support bracket 38, having one leg thereof affixed to the underside of the table 13, includes openings in the respective legs through which the shaft 32s extends. The limits of vertical travel for the shaft 32s, and in turn the oven assembly 32, are determined by collar stops 38a aflixed about the shaft 32s in the manner shown. A resilient helical spring 37 is insertable over a bottom portion of the shaft 32s, bearing against the bottom leg of the bracket 38 and the top one of the collar stops 3801, thereby providing a bias for the oven assembly 32 in the upward direction. Thus, with this construction, the tipotf oven assembly 32 is seen to be rotatable about the shaft 32s for horizontal alignment and movable in a vertical direction against the action of the spring 37 between the limits as set by the respective collar stops 38a.

The exhaust chuck assembly 30 includes a cylindrical, hollow chamber 30a, open at the top and externally threaded about the rim to receive an associated cap or cover 40. A shoulder or flange 42 is selectively positioned internally of the chamber 30a, e.g., approximately a third of the distance down from the top. The flange 42 includes a central opening 42a to permit the tubulature 24t to pass therethrough, as shown in FIGURE 2. The flange 42 serves to support a block of resilient material 43, such as rubber, which is cylindrical in shape to fit snuggly in the chamber opening above the flange 42. The function of the rubber block 42 is to serve as a seal when the tube 24 is being evacuated. The rubber seal 42 includes a central opening dimensioned to receive the tubulature 24t therethrough with minimum clearance but without binding. The rubber seal 42 extends slightly above the top edge of the chamber 30a so that when the cap 40 is screwed down tightly, the seal 42 is spherically compressed between the cap, flange and side walls. The result is that an effective seal is provided along the length of the tubulature 24t in contact with the sides of the central opening in the seal 43.

The tube itself is evacuated by the vacuum pump 16 connected to the chamber 30a by the airline 44 composed of copper line or the like which is coupled into the chamber 30a by an airtight connector assembly 45. A petcock 46 may be provided at the bottom of the chamber 30a to drain off moisture condension that may collect during the evacuation processes for the cathode ray tubes. The chamber 30a is suitably affiixed to the table top 13, such as by angle brackets 47 or the like.

In the fully lowered position, in which position the cathode ray tube 24 may be evacuated, the tubulature 242 extend-s through the central opening of the rubber seal 43 into the lower compartment of the chamber 39a. In this position, best seen in FIGURE 2, the pins of the tube 24 are received in the associated pin receptacles of the tip-oven assembly 32 and the R-F coil assembly 34 is positioned adjacent the gun assembly of the tube 24. With the tube 24 in this position, the entire cart may be passed through an oven chamber (not shown) wherein the gasses may be driven from the various internal parts. In addition, the R-F coil assembly 34 may provide relatively intense heat locally about the gun assembly 24g. At an appropriate time, the tip-off oven assembly 32 is energized so as to provide a relatively intense heat locally to a portion of the tubulature 24t, such as that indicated by the cross-hatch area 24x in FIGURE 3, whereby the area collapses inwardly under action of the vacuum and effectively seals off the tube when it is allowed to cool and solidify.

After the tip has been sealed, the tip-off oven 32 is depressed downwardly and the sealed portion of the tubulator 241 is scratched with a file or the like and broken off. The sealed-off tubulator portion may be left in the exhaust chuck assembly until the tubulator of a new cathode ray tube is to be inserted.

The improved tube lift mechanism constructed in accordance with the present invention is indicated generally at 50, best seen in FIGURES 4 and 5. The lift 50 includes a pair of vertical members 52 suitable affiXed to the underside of the table 13 and extending downwardly at opposing sides of the frame 11. A pivotable lever arm 54 is suspended on the bottom end of each of the members 52. The arms 54 are attached intermediate their ends by a pivot pin 55. The lever arms 54 and the vertical members 52 may be conveniently formed from conventional angle bracket stock or other materials may be used if desired.

Each of the lever arms 54 includes a roller 56 at the one end thereof adjacent to the bottom end of the vertical support columns 22. A mounting bolt or pin 56a secures the rollers 56 to the lever arms 54 and serve as axles therefor. The opposite ends of the lever arms are utilized to support a counter-weight 58 therefrom (FIGURES 1, 4 and 5). In this embodimengthe counterweight 58 includes a pair of flanges or tabs 58a extending upwardly at respective ends of the counterweight and substantially normal to the longitudinal axis thereof. Mounting bolts or pins 58b extend through suitable clearance holes provided in the arms 54 and the tabs 58a whereby the counterweight 58 is pendulously supported in the manner shown in FIGURES 1, 4 and 5. That is, the counterweight 58 is thus allowed to swing about the pivot points formed by the pins 58b as the lever arms 54 are pivoted about the pivot pin 55. The result is that the center of gravity of the counterweight 58 is maintained in continuously vertical alignment with the pin 58b at all set positions for the tube lift mechanism 50.

At the other end of the lever arms 54, the vertical support columns 22 include a flat base section 220 which has a horizontal dimension sufficient to ensure that a portion thereof overlays the center of the roller 56 at any set position of the lever arms 54. The base 220 thus contacts the roller 56 at a single point on the periphery thereof, a point which is at all times in vertical alignment with the pivot pin 56a acting as the axle. The result is that the weight of the tube 24 and the vertical support columns 22 produce a force which is always acting directly on the pin 56a.

It will be appreciated that a moment of force is produced at the respective ends of the lever members 54 which act directly on the end pivot points as represented by the pivot pins 56a and 58b. The result is that for a given counterweight 58 and cathode ray tube 24, a balance is maintained for the tube lift mechanism 50 at all set positions because of the moments produced at

pivot pins

56a and 58b being substantially equal.

This all-point balance would not occur, however, if the counterweight 58 were not pendulously supported about the pivot pin 58b, but were rigidly and non-rotatably suspended from the end of lever members 54. In the latter condition, the center of gravity of the counterweight 58 would not be maintained in direct vertical alignment wit-h pivot pin 58b but would be progressively shifted therefrom to one side or the other as the tube lift mechanism 50 is moved from the completely horizontal position. This can be more readily appreciated by reference to FIGURE 8. As the lever member 54 is moved downwardly from the horizontal position H to one such as indicated as HV, it will be seen that the counterweight 58 swings counterclockwise from a position perpendicular to lever member 54 to one forming an obtuse angle thereto, thereby maintaining the center of gravity of the counterweight 58 in direct vertical alignment with the pivot pin 58b. Should the counterweight 58 be nonrotably suspended from the lever member 54, and thus remain in a position perpendicular thereto as in the fully horizontal position H, the center of gravity for counterweight 58 would be shifted, when viewing FIGURE 8, to a position along the dotted line X when moved to the position HV. This shifting of the center of gravity to the left would thus produce a moment of force which would be less than that as produced by the vertical columnar supports 20 and the cathode ray tube 24 acting on the came roller 56, and in turn, on the pivot pin 56a, thereby creating an imbalance in the system.

It is not, however, to be inferred from the foregoing that only cathode ray tubes of one specific and definite weights may be accommodated for a given counterweight. 0n the contrary, one of the advantages of the tube lift mechanism constructed in accordance with the present invention is that cathode ray tubes within a predetermined range of weights may be vertically positioned by the tube lift mechanism 50 with smoothness and accuracy without further adjustments of any kind being necessary. Any difference in weight between the counterweight 58 and a particular cathode ray tube 24 (within the aforesaid weight range) that may be present is effectively compensated for by frictional forces introduced into the system, principally by the interaction of the sleeve guides 20 with the vertical support columns 22. In the preferred form, the guides 20 telescopically receive the columns 22 therein, respectively, and are constructed so as to provide a friction interfit therebetween. This friction interfit between guide 20 and vertical column 22 provides a predetermined resistance to movement which must be overcome in order to effect any change of position for the lift mechanism 50 and is effective to maintain the mechanism 50 in its set position despite a difference in weight between counterweight 58 and a cathode ray tube 24 supported by column elements 22. It is to be emphasized, however, that the value or degree of clearance between the guides 20 and column elements 22 is not critical and may be varied within limits without departing from the true scope of the present invention. Moreover, other frictional forces may likewise be introduced into the system from other sources to supplement that as provided by the guides 20 and column elements 22. For example, additional resistance to movement may be provided at the pivot points 55, 56a and 58b if desired.

With a tube lift mechanism 50 thus described, cathode ray tubes of differing weights may be effectively accommodated without additional or further adjustment being necessary. In practice, it has been found that cathode ray tubes having a surprisingly large variation in their weights may be vertically located in any desired set position on the portable exhaust cart 10 with comparative smoothness and accuracy. A cathode ray tube 24 with a higher weight will produce a sinusoidal moment characteristic which is shifted upwardly and a tube with less weight will produce such a curve shifted downwardly. However, as long as the difference between the moment characteristic of the tube 24 plus columnular elements 22 and the moment characteristic of the counterweight 58 does not exceed the resistance to movement effected by the friction interfit between guides 20 and columns 22, the mechanism 50 will remain in that position when so set. No further adjustments of any kind are necessary to compensate for the differing weights of the cathode ray tubes within this predetermined range.

The support columns 22 are preferably constructed of a rust-resistant material, such as stainless steel, or the like, while the sleeve guides 20 may be formed from common cold rolled steel stock, since the inner bearing surface contacting the columns 22 are not exposed to the ambient atmosphere. Other materials may be used, of course, without departing from the true scope of the present invention.

It is also to be emphasized that the frictional interfit between the guides 20 and columns 22 additionally serves to provide the unusual smoothness of vertical movement as well as the capability of effecting relatively small increments of such movement which characterize the lift mechanism of the present invention. In order to change the position of the mechanism 50, a certain minimum force must be applied, that is, a force which exceeds the resistance to movement caused by the friction, plus or minus the difference between the moments of force being produced at opposing ends of the lever members. This will be seen to effect more uniform acceleration and de-acceleration for the lift mechanism as a unit and thereby minimize overshoot and the inherently jerky motion ordinarily to be found in the more free-swinging systems. This minimizing of the overshoot is quite essential in the ability of the left mechanism to effect small increments of vertical movement for the positioning of the cathode ray tubes 24.

From a purely theoretical viewpoint, it cannot be said with absolute certainty the precise factors giving rise to the unusual smoothness of the operation exhibited by the lift mechanism of the present invention and the accuracy with which a cathode ray tube may be vertically positioned upon the exhaust cart. An important contributing factor, however, must necessarily reside in the fact that the lift mechanism 50 maintain a dynamic balance as well as a static balance. This dynamic balancing effect arises from the fact that the counterweight 58, in being pendulously supported as previously described, always swings counter to the arc of rotation imparted to the lever members 54. That is, as the lever members 54 are pushed downwardly (viewing FIGURE 8), thereby tending to impart a clockwise rotational are to counterweight 58, the force of gravity operates to swing the counterweight 58 in a counterclockwise direction from its position perpendicular to lever member 54 when in the fully horizontal position to one which maintains its center of gravity in vertical alignment with pivot pin 58b. The result is that the angular momentum that would otherwise be imparted to counterweight 58 is thus compensated for or negated and overshoot of the lift mechanism 50 thereby effectively avoided or minimized. This compensation characteristic becomes particularly advantageous for counterweights of significant mass and weight and in instances when it is desired to move the lift mechanism 50 at a rapid rate from one set position to another.

Cathode ray tubes of increasing weight ranges, as previously mentioned, may also be accommodated by the lift mechanism 50. That is, tubes having a weight which produces a moment of force at one end of each of the lever members 54 which exceeds the moment of force produced by the counterweight 58 at the opposing ends thereof by an amount greater than the resistance to movement presented by the frictional interfit between the guides 20 and columns 22. To this end, the counterweight 58 may be constructed so as to include a hollow core extending along a substantial part of its longitudinal dimension and having an opening at one end, as shown in FIGURE 7. A cap 580 may be threadably received on the threaded open end. By inserting additional weights, such as the Weight 59, into the core of the counterweight 58, a moment characteristic curve will be obtained which will be shifted upwardly from that of the curve 62 in FIGURE 8say, for exampleone which approaches that of curve 66. The additional weights are constructed with a cylindrical shape so as to roll or rotate within the core of the counterweight 58 under the action of gravity. As a result, the same non-sinusoidal moment characteristic is obtained as shown for the counterweight 58 alone in the curve 62.

Additionally, it may be observed that as long as the additional cylindrical weights, such as that represented by the weight 59, are free to roll or rotate with the hollow core, it is not essential that the counterweight 58 be maintained in its above described pendulously supported, free-swinging relation to the lever members 54, but, alternatively, may be rigidly attached thereto if so desired. Such an embodiment is shown in FIGURE 10. In its preferred form, the counterweight 58 is rigidly secured to the lever members 54, as by welding the support tabs 58a thereto, in a manner to hold the counterweight in a selected position or angle to the members 54. The counterweight 58 is thus nonrotatable as contrasted to being permitted to rotate or pivot about the mounting bolt 58b, as described in connection with FIGURES 4 and S. In the embodiment of FIGURE 10, it will be seen that the same relative position is maintained at all vertically set positions for the lift mechanism 50. If desired, a handle 68, shown in phantom line, may be secured to the end of one of the lever members 54 to facilitate positioning of the lift mechanism 50.

With the construction as shown in FIGURE 10, the added weight 59 inserted in the core of the counterweight 58 shifts within the core under the influence of gravity so as to produce a similar nonsinusoidal moment characteristic at one end of the respective lever members 54 as that represented by the moment curve 62.

While only certain specific embodiments of the invention are shown and described herein, it will, of course, be understood that many variations and modifications may be effected without departing from the true spirit and scope of the invention. The appended claims are intended to cover all such modifications and alternative constructions that fall within their true scope and spirit.

What is claimed is:

1. In a portable exhaust cart, a tube lift mechanism for locating a cathode ray tube having a weight within a predetermined range in a selected vertical position within predetermined limits, said lif-t mechanism including in combination:

a frame;

a pair of vertical sleeve guides mounted on said frame;

a pair of vertical support columns, each of said columns being telescopically received within an associated sleeve guide, said sleeve guides and said vertical support columns having a close-tolerance interfit therebetween;

yoke means affixed to said columns at one end thereof in tube-receiving relation to support the cathode ray tube therebetween;

lever means pivotably suspended from said frame intermediate its ends, said lever means including camming means at one end and a reference point at the opposite end, said camming means engaging said support columns at an end opposite the end at which said yoke means is afiixed so as to support said vertical columns and cathode ray tube and to impart vertical movement thereto when said lever means is pivoted; and

counterweighting means, said counterweighting means being positioned at said opposite end of said lever means adjacent said reference point, said counterweighting means exerting a balancing force acting directly on said reference point at all set positions of the lift mechanism,

said close-tolerance interfit between said sleeve guides and vertical support columns providing a frictional force effective to resist movement of the lift mechanism when at rest and maintain the same at any set position notwithstanding a difference between the force exerted by said counterweighting means and that by the vertical support columns and cathode ray tube Within said predetermined weight range.

2. A mechanism to locate an object having a weight within a predetermined range in a selected vertical position within predetermined limits, comprising in combination:

a frame;

vertical support means on said frame to support said object, said means including columnar elements movable between said predetermined limits;

lever means pivotably supported on said frame intermediate its ends, said lever means having a substantially horizontal axis and an end portion engaging a portion of said columnar support elements to impart vertical movement thereto for positioning said object;

a counterweight mounted at a reference point on the side of said lever means opposite said one end portion, said counterweight being carried by said lever means in a manner whereby the center of gravity thereof is maintained in substantial vertical alignment with said reference point at all set positions of the mechanism;

and frictional guide means, said guide means receiving said columnar support elements and having an interfit therewith effective to resist movement of said lever means when at rest and hold the same at any set position within said predetermined limits.

3. A tube lift mechanism for vertically locating a cathode ray tube having a bell portion, a neck portion and a weight in a predetermined weight range, with smoothness and accuracy, comprising in combination:

a frame;

vertical support means for supporting said cathode ray tube and including a yoke portion to engage the bell portion of the tube and support the same and vertically extending column elements;

guide means on said frame to orient the column elements of the support means in tube-receiving position while permitting vertical movement thereof, said guide means and said column elements having a frictional interfit therebetween;

lever means rockable about a substantially common,

substantially horizontal axis, said lever means including an end portion engaging column elements to impart vertical movement thereto for positioning said cathode ray tube;

a counterweight;

means pendulously supporting said counterweight from said lever means on the side opposite said one end portion;

said frictional interfit between said guide means and said column elements being such as to overcome any imbalance in the lift mechanism system between the counterweight and any tube weight within said predetermined range.

4. A tube lift mechanism for vertically locating a cathode ray tube having a bell portion, a neck portion and a Weight in a predetermined range, with smoothness and accuracy, comprising in combination:

a frame; support means adapted to seat on the bell portion of the tube and support the same vertically, said support means having vertically extending column elements;

lever means rockable about a substantially common,

substantially horizontal axis, said lever means including an end portion engaging said column elements to impart vertical movement thereto for positioning said cathode ray tube;

an elongated and substantially cylindrically shaped counterweight; and

means supporting said counterweight from said lever means on the side opposite said one end portion, with its longitudinal axis substantially parallel to but trans verse said horizontal axis of said lever means,

said frictional interfit between said guide means and said column elements being such as to overcome any imbalance in the lift mechanism between the counterweight and any tube weight within said predetermined range,

said counterweight having a hollow core wherein additional weights are insertable to permit the accommodation of tubes having weights within a range higher than the aforesaid predetermined weight range.

5. A tube lift mechanism for vertically locating a cathode ray tube having a bell portion, a neck portion and a weight in a predetermined range, with smoothness and accuracy, comprising in combination:

a frame;

support means including a yoke portion adapted to seat on the bell portion of the tube to support the same vertically, said support means further having vertically extending column elements;

lever means rockable about a substantially common,

an elongated counterweight; and

means supporting said counterweight from said lever means on the side opposite said one end portion with its longitudinal axis substantially parallel to but transverse said horizontal axis of said lever means,

said counterweight having a hollow cylindrically shaped core wherein additional cylindrically-shaped weights are insertable so as to rotate within the core under the influence of gravity,

said frictional interfit between said guide means and said column elements being such so as to maintain the lift mechanism in any set position despite a difference in weight between said counterweight and the cathode ray tube within said predetermined weight range.

References Cited UNITED STATES PATENTS 969,324 9/1910 Bachman 248292 X 1,942,925 1/1934 Jenkins 248292 X 2,273,439 2/ 1942 Freeman 65155 X 2,886,336 5/1959 Reynard 65-155 X ROY D. FRAZIER, Primary Examiner. J. F. FOSS, Assistant Examiner.

Claims

1. IN A PORTABLE EXHAUST CART, A TUBE LIFT MECHANISM FOR LOCATING A CATHODE RAY TUBE HAVING A WEIGHT WITHIN A PREDETERMINED RANGE IN A SELECTED VERTICAL POSITION WITHIN PREDETERMINED LIMITS, SAID LIFT MECHANISM INCLUDING IN COMBINATION; A FRAME; A PAIR OF VERTICAL SLEEVE GUIDES MOUNTED ON SAID FRAME; A PAIR OF VERTICAL SUPPORT COLUMNS, EACH OF SAID COLUMNS BEING TELESCOPICALLY RECEIVED WITHIN AN ASSOCIATED SLEEVE GUIDE, SAID SLEEVE GUIDES AND SAID VERTICAL SUPPORT COLUMNS HAVING A CLOSE-TOLERANCE INTERFIT THEREBETWEEN; YOKE MEANS AFFIXED TO SAID COLUMNS AT ONE END THEREOF IN TUBE-RECEIVING RELATION TO SUPPORT THE CATHODE RAY TUBE THEREBETWEEN; LEVER MEANS PIVOTABLY SUSPENDED FROM SAID FRAME INTERMEDIATE ITS ENDS, SAID LEVER MEANS INCLUDING CAMMING MEANS AT ONE END AND A REFERENCE POINT AT THE OPPOSITE END, SAID CAMMING MEANS ENGAGING SAID SUPPORT COLUMNS AT AN END OPPOSITE THE END AT WHICH SAID YOKE MEANS IS AFFIXED SO AS TO SUPPORT SAID VERTICAL COLUMNS AND CATHODE RAY TUBE AND TO IMPART VERTICAL MOVEMENT THERETO WHEN SAID LEVER MEANS IS PIVOTED; AND COUNTERWEIGHTING MEANS, SAID COUNTERWEIGHTING MEANS BEING POSITIONED AT SAID OPPOSITE END OF SAID LEVER MEANS ADJACENT SAID REFERENCE POINT, SAID COUNTERWEIGHTING MEANS EXERTING A BALANCING FORCE ACTING DIRECTLY ON SAID REFERENCE POINT AT ALL SET POSITIONS OF THE LIFT MECHANISM, SAID CLOSE-TOLERANCE INTERFIT BETWEEN SAID SLEEVE GUIDES AND VERTICAL SUPPORT COLUMNS PROVIDING A FRICTIONAL FORCE EFFECTIVE TO RESIST MOVEMENT OF THE LIFT MECHANISM WHEN AT REST AND MAINTAIN THE SAME AT ANY SET POSITION NOTWITHSTANDING A DIFFERENCE BETWEEN THE FORCE EXERTED BY SAID COUNTERWEIGHTING MEANS AND THAT BY THE VERTICAL SUPPORT COLUMNS AND CATHODE RAY TUBE WITHIN SAID PREDETERMINED WEIGHT RANGE.