X-ray apparatus including counterbalancing mechanism for spot filmer or the like

Abstract

X-ray table and spot filmer arrangement in which two to one mechanical advantage is obtained on counterweights to reduce weight requirements and rectilinear parking of the spot filmer is obtained.

Parent Case Text

This is a continuation, of application Ser. No. 656,448, filed July 27, 1967, now abandoned.

Description

CROSS REFERENCED APPLICATIONS AND PATENTS

1. Barrett et al., U.S. Pat. No. 3,173,008, issued Mar. 9, 1965 under the title "Spot Filmer".

2. R. C. Schiring et al., U.S. Pat. No. 2,872,584 issued Feb. 3, 1959 under the title "X-Ray Apparatus".

3. R. C. Schiring, U.S. Pat. No. 2,997,585 issued Aug. 22, 1961 under the title "Combined Image Amplified and Fluoroscopic Screen Above X-Ray Examination Table."

4. Future application entitled "Automatic X-Ray Shutter Control" by E. A. Norgren.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is directed to X-ray apparatus and more particularly to X-ray tables on which a spot filmer or the like is mounted. In X-ray examination mechanisms, it is now well-known to provide a so-called 90-90 X-ray table in which a table body is tiltable on its pedestal in either direction 90.degree. from a position where the table top is horizontal. Thus, the body of the table may be moved clockwise or counterclockwise from the horizontal until its top is vertical or to any position between the two vertical positions. One such table is that described and claimed in the referenced Schiring et al. U.S. Pat. No. 2,872,584.

Other tables with lesser amounts of tilting are also known. Some tables, for example, have a body which is tiltable in one direction from a position with the top horizontal to a vertical position and in the other direction to a so-called Trandelenburg position wherein the angle of the table top is approximately 15.degree. with the horizontal.

In many of the described prior tables, a guide track which parallels the table top is provided. A movable column or tower is reciprocably mounted on the track for movement in a path of travel which is longitudinal with respect to the top. The column is also mounted for reciprocal rectilinear movement along a guide path which is transverse to the top and normal to the column travel along the guide track.

The usual column supports and X-ray tube which is positioned beneath the table top and within the table body. One or more image-producing X-ray responsive devices such as a spot filmer or an image intensification device are supported by a carriage. The carriage is reciprocally mounted on the column for travel along a rectilinear path which is perpendicular to the table top.

These three rectilinear paths of travel permit the carrier to be moved to any selected position over the table top and to any selected distance from the top within the limits of the respective paths of travel.

Since the movement of the carrier relative to the column is vertical movement when the table top is horizontal, counterbalancing weights are carried in the column to facilitate the vertical movement of the carrier. Thus, one pound of weight in the carrier will, with a one-to-one mechanical advantage, mean one pound of counterweight and therefore two pounds of carrier and column weight.

Since the column is movable in a vertical path when the table top is in a vertical position, weights to counterbalance the column are provided in the table. The tower or column counterbalancing weights must include one pound for each pound of carrier weight. Thus one pound for each pound of carrier and one for each pound of counterbalancing weight. With a one-to-one mechanical advantage in the counterweights carried in the table body as well as those in column, it will be seen that for every pound of weight on the carrier, three pounds of counterbalancing weight must be added to the table.

With such equipment as an image intensification tube and a camera mounted on the carrier in addition to a spot filmer, counterbalancing has become a problem. In many situations, the maximum limit of counterweight which can be added to the table has been met.

One solution for assisting in this counterbalancing problem is to provide ceiling-mounted counterbalances which support weight of a spot filmer or other devices mounted in the column. One such ceiling counterweight is described in U.S. Pat. No. 2,997,585 issued Aug. 22, 1961 to R. C. Schiring and entitled "Combined Image Amplifier and Fluoroscopic Screen above X-Ray Examination Table."

Another problem that has existed in the prior art is that of so-called "parking" of an imaging device such as a spot filmer. There are certain procedures where an X-ray tube supported either on a "bi-rail" device or by a ceiling mount is positioned above the patient. A film positioned in a so-called Bucky tray within the table body is then exposed. In order to conduct studies with an overhead tube, it is desirable that the spot filmer be moved away from the patient to free completely the space above the patient.

2. Prior art

One prior arrangement for parking a spot filmer has been a pivot connection of it to the vertical column or tower so that it may be pivot upwardly to a relatively out-of the-way position when not in use. While this has in the past been reasonably suitable, with the increasingly common use of image intensification tubes connected to the spot filmer and with greater weight in the spot filmers, this becomes disadvantageous both because of the weight of the spot filmer and the supported mechanism, and because of the limited amount of pivoting which can be obtained when an image tube and associated equipment such as a cine camera are mounted on the top of the spot filmer.

There in the past have been proposals for so-called spot filmer parking where the spot filmer is moved rectilinearly rearwardly into its parking position. The problem that has been experienced, however, is that with the amount of counterbalancing required in the tower, clearnace which permits the spot filmer to be parked rectilinearly has not been obtainable with the coutnerweights in the tower. With one system used to overcome this problem when reciprocal parking has been provided, the counterweights for the imaging device and its carriage have been carried in the table and a pulley and cable arrangement has been provided to interconnect the counterweights and the spot filmer.

Even though there have been a few prior attempts at providing so-called doubling arrangement to reduce the amount of counterweight required, neither those proposals nor any other prior art proposal has suggested an arrangement wherein the counterweights can be positioned in the tower in a system where a spot filmer or other imaging device can be parked by rectilinear motion over the top of the tower.

SUMMARY OF THE INVENTION

The present invention provides a novel counterweighting system and parking arrangement for image devices. Typical imaging devices are the spot filmers which have been mentioned and frame structures the size of spot filmers which carry X-ray sensitive image intensification tubes. The invention will be described in conjunction with a spot filmer as exemplary of imaging devices.

With this invention, an intermediate carriage is provided. The intermediate carriage supports, through a pulley arrangement, a counterweight and is connected to a pulley arrangement to which the spot filmer is connected. As a spot filmer is brought down, the intermediate carriage rises the same amount. The counterweight carried by the carriage moves upwardly relative to the carriage the same amount as the spot filmer movement and this, coupled with the intermediate carriage movement, produces movement of the counterweight twice that of the spot filmer. With twice the movement and a mechanical advantage attendant to it, approximately one-half the normal weight required for counterbalancing is utilized.

When the spot filmer is raised to its parked position, the intermediate carriage and the counterweight are lowered concurrently to storage positions. The outstanding advantage of reciprocal or rectilinear parking at a convenient height and level is achieved by providing a table column which is open at the top. When the spot filmer is fully lowered, the intermediate carriage and the counterweights carried by it project upwardly out of the column. When the spot filmer is at its top parked position, the carriage and counterweight are in their storage positions which are within the column. This permits facile parking of the spot filmer above the column at the convenient and relatively low height.

Another feature of the invention resides in a novel latching arrangement which, among other advantages, positively prevents any vertical spot filmer movement until the filmer is fully out of its parked position.

Accordingly, the object of this invention is to provide, in an X-ray table equipped with a tower and spot filmer or similar device on it, a parking arrangement which is rectilinear in combination with a counterweighting arrangement which is doubling arrangement to reduce the amount of weight required.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing fragmentary portions of an X-ray table, a column on the table, and a spot filmer in the parked position achieved with this invention;

FIG. 2 is a rear elevational view of the column, showing in dotted lines the intermediate carriage and the pulley arrangement;

FIG. 3 is a top plan view of the table column, the intermediate carriage and the counterweighting arrangement;

FIGS. 4 and 5 are sectional views as seen respectively from the planes indicated by the lines 4--4 and 5--5 of FIG. 2;

FIGS. 6 and 7 are diagrammatic views showing the pulley arrangement embodiment within the table column;

FIG. 8 is a sectional view of the carriage for the imaging device used with this invention, showing a partially sectioned view of one of the image device tracks in its parked position, fragmentary views of the mast tracks, and a plan view of a latching device;

FIG. 9 is a fragmentary sectional view corresponding to the upper portion of FIG. 10, showing the imaging device track in a transitory position between the park and operating positions; and,

FIG. 10 is a view corresponding to FIG. 9 showing the imaging device track in its operating position.

Referring to the drawings and to FIG. 1 in particular, a fragmentary portion of the table body is shown generally at 10. The table body includes a top 11, which, in the embodiment shown, is movable along tracks 12. The table body carries a tower shown generally at 14. The tower 14 includes a horizontal carriage portion 15 which is supported on the usual tracks within the table body 10 for rectilinear movement parallel to the table top 11. The carriage portion 15 is mounted for reciprocal movement both transverse with respect to the table top and longitudinal with respect to the table top so that the spot filmer shown generally at 17 can be positioned at any location over the table top 11.

The tower includes a vertical mast 18 which is equipped with guide tracks 19, 20, 20a on which a support carriage 21 for the spot filmer or other imaging device is mounted. Rollers 16 carried by the spot filmer carriage 21. FIG. 8, permit the spot filmer carriage to move rectilinearly along the tracks 19, 20, 20a in a path toward any away from the table top 11.

The spot filmer 17 has horizontal tracks 22, FIG. 1, which coact with rollers 23, FIG. 8, within the spot filmer carriage 21. These rollers permit the spot filmer 17 to be shifted rectilinearly along a path paralleling the table top from the parked position shown in FIG. 1 to a forwardly extended position over the table top. In its forwardly extended position, the spot filmer is completely forward of the tower and mast portion 18.

The spot filmer 17 may be of the type described in the above-identified Barrett et al. patent. It includes a front load opening indicated by the arrow 24 through which a cassette containing film may be inserted and withdrawn. It also includes the usual shutter controls 25, a switch for turning on magnetic locks 26, an exposure control button 27, a positioning handle 28, and other allied structure which will be readily recognized by mechanism skilled in the art.

Referring now to FIGS. 6 and 7, the spot filmer 17 and its carriage are indicated in Phantom lines. The spot filmer carriage is connected at 30 to a first or mast endless cable 31. The mast cable 31 is reeved over mast pulleys 32 which are, as will be explained presently, journaled in the mast 18.

An intermediate carriage 33 is provided. The intermediate carriage 33 is connected at 34 to mast cable 31. With this construction, as the spot filmer is lowered from the position shown in FIG. 6 to the position shown in FIG. 7, the connection at 30 of the spot filmer to the mast cable 31 will shift the cable causing the mast pulley 32 to rotate in a clockwise direction. This action simultaneously causes the connection 34 of the intermediate carriage 33 to rise and the intermediate carriage 33 to rise from the position of FIG. 6 to that of FIG. 7 in a manner which will be described in more detail presently.

The intermediate carriage 33 carries carriage pulleys 35. A second or carriage endless cable 37 is reeved around the carriage pulleys 35. The carriage cable 37 is anchored at 36 to the frame of the mast 18.

A counterweight carriage assembly composed of counterweights and a counterweight carriage is indicated by the numeral 38. The counterweight assembly is mounted by rollers 39 on the intermediate carriage 33 for movement relative to it. The counterweight carriage is connected at 40 to the carriage cable 37.

Since the carriage cable 37 is anchored to the frame at 36, movement of the intermediate carriage 33 upwardly due to downward movement of the spot filmer 17 will cause the carriage cable 37 to move a distance relative to the carriage equal to the amount of movement of the mast cable 31. Expressed another way, the carriage pulleys 35 will rotate clockwise the same amount as the mast pulleys 32. Since the counterweight assembly 38 is mounted on the intermediate carriage it will obviously move with the intermediate carriage by that amount. Since it is connected at 40 to the carriage cable 37 which is moving relative to the intermediate carriage 33, the counterweight assembly 38 is also caused to move upwardly relative to the intermediate carriage. The total of these two movements of the counterweight assembly results in its moving a distance twice that of the spot filmer 17. Since the amount of movement is twice that of the spot filmer 17 the amount of weight needed to counterbalance the spot filmer is essentially one-half that of the spot filmer, friction in the system causing it to be slightly different than one-half.

Referring now to FIGS. 2-5, the components there corresponding to those described in connection with the schematic showing of FIGS. 6 and 7 are identified by like numerals. In the actual construction, there are four endless cables, two mast cables 31 mounted on opposite sides of the mast, and two carriage cables 37 carried by the intermediate carriage 33.

The four mast pulleys 32 are journaled on flanges 45 which are fixed to the mast 18. The pulleys 32 are journaled for rotation about axes which parallel the transverse dimension of the table. To insure against any possible slippage each mast cable 31 is actually made of two portions of equal length. One end of each of the portions is anchored at 34 on the intermediate carriage 33. The other ends, not shown, are similarly anchored on the spot filmer after being reeved about a snub bar identified in FIGS. 4 and 5 by the numeral 30 to designate the connection of the cable 31 to the spot filmer carriage.

The intermediate carriage 33 includes a vertical plate portion 47 which forms its back. The intermediate carriage has a base portion 48 which is horizontally disposed and which may be formed by bending a plate to provide both the back and the base portions. The base portion 48 has an opening at 49 through which part of the counterweight assembly may project when in the lowered or storage positions. The base portion 48 also carries the pair of bumpers 50 of rubber or similar material, only one of which is visible in FIG. 4. These bumpers 50 engage the counterweight assenbly 38 when it is in its fully lowered position as shown in FIG. 5.

The intermediate carriage 33 has side portions 52, 53, FIG. 3, which project forwardly from the back portion 47 and are perpendicular to it. The side portions 52, 53 carry mounting flanges 54, 55 which project horizontally outwardly. The mounting flanges 54, 55 carry two pairs of carriage rollers 56, 57. The carriage rollers 56, 57 engage mast tracks 59, 60 carried on the sides of the mast. The engagement of the rollers 56, 57 in the tracks 59, 60 provides guiding movement.

In FIGS. 2-5 counterweight carriage 61 of the counterweight assembly 38 is shown but the counterweight themselves are omitted for clarity of illustration. The counterweight carriage 61 includes a horizontally disposed platform portion 62 upon which counterweights may be mounted. The platform 62 extends on either side of a vertical support portion 63 of the counterweight carriage. The counterweight carriage 61 includes a horizontal pair of flanges 64 to which the endless cables 37 are connected at 40. The counterweight carriage rollers 39 are journaled on the vertical support plate portion 63 and positioned to engage guide tracks 65, 66 which are provided on the side portions of the intermediate carriage 33.

A pair of cable anchor brackets 67 are provided on opposite sides of front wall 68 of the mast 18. The brackets 67 have bolts extending therethrough to provide the anchor 36 for the endless cable 37. To assist in effecting this anchoring of the cable 37, snubs 69 are provided and secured near the tops of the bracket 67.

Spot Filmer Parking

In FIGS. 8-10, fragmentary sectional views of the spot filmer carriage 21 are shown. In addition, one of the spot filmer tracks 22 is visible in each of the views and portions of the mast tracks 19, 20 are shown.

A spot filmer position latch 70 is provided. The position latch is pivotally mounted at 71 on the spot filmer carriage 21. The position latch 70 selectively engages either a park position notch 72 or an operating position notch 73. The notches 72, 73 are formed in the spot filmer guide track 22. A latch groove 74 extends from one notch to the other so that the upper portion of the position latch 70 remains partially disposed within the spot filmer track 22 at all times in a manner which will be described in more detail.

The parked position notch 72 has its forward surface defined by a reciprocally movable latch bumper 76. The latch bumper 76 can move forwardly, to the right in FIGS. 8-10, against the resilient compression of a cushion 77 carried within the track 22. Thus, when the spot filmer reaches the park position shown in FIG. 8 and the latch 70 engages the bumper 76 to stop the parking movement, the stopping action is cushioned by the sliding movement of the latch bumper 76 acting against the latch cushion 77. Similarly, when the spot filmer is moved rectilinearly forward to its operating position, sliding movement of a latch bumper 78 against another latch cushion 79 cushions the stopping action of the spot filmer as it reaches its forward operation position.

When one wishes to move the spot filmer from the park position shown in FIG. 8 forwardly to the operating position of FIG. 10, a latch release button 80 is depressed. As the latch button 80 is depressed a button pin 81 compresses a button spring 82. As soon as the button is released the spring 82 acting against the pin 81 will return the button to the position shown in FIG. 8.

The pressing of the latch button 80 causes a latch pivot link 83 to pivot about its mounting 84 on the spot filmer carriage 21. A latch actuating link 85 is pivotally connected to the latch 70 and to the pivot link 83. The pivoting of the latch pivot link 83 shifts the latch actuating link 85 rearwardly causing the position latch 70 to pivot about its pivot 71. This pivoting of the latch 70 lowers the latch sufficiently to permit the spot filmer to be pulled forwardly while the top portion of the latch 70 is in the latch groove 74.

The spot filmer 17 must be at the top of its travel before it can pass over the tracks 20, 20a to the parked position. The spot filmer is maintained in its upward position when it is parked. The maintenance of th spot filmer in this upward position is provided by a vertical position link 87. The vertical position link 87 overlies and engages the top of track 20 when the spot filmer carriage 21 is in the park position and substantially at the top of its travel.

A vertical position control link 88 is connected to the vertical position link 87 and to the position latch 70 by lost motion connections 89, 90 respectively. At the time when the spot filmer is being brought forwardly from its park position of FIG. 8 to its operating position of FIG. 10, the weight of the spot filmer holds the vertical position link 87 in engagement with the top of the mast track 20. When this engagement exists, depression of the release button 80 and the resultant movement of the position latch 70 has no effect on this vertical holding action of the vertical link 87. This is accomplished by the lost motion connections 89, 90 which permit this movement of the latch 70 while the vertical link 87 remains stationary.

Once the spot filmer has reached the forward position shown in FIG. 10, a latch spring 92 will pivot the latch 70 about its pivot 71, causing the top portion of the latch to move into and engage the notch 73. This engagement of the link 70 with the notch prevents rearward movement of the spot filmer until such time as the spot filmer is raised fully and the button 80 is depressed. Again, because of the lost motion connections 89, 90, this latch action can occur without the vertical position link 87 leaving its position engaging the top link 20. Slight upward manipulation of the spot filmer will lift the vertical link 87 off the top of the track 20.

A limit switch 95 is provided. The limit switch is a normally open switch which is depressed by the vertical link 87 when it is forward of the track 20. Depressing of the limit switch 95 closes it enabling an X-ray exposure to be taken. Whenever the link 87 is in its position over the track 20, the limit switch 95 is open serving as a safety precaution by preventing an X-ray exposure from being taken.

The shifting of the spot filmer from its operating position of FIG. 10 to the park position of FIG. 8 is the reverse of the operation thus far described. The spot filmer is first elevated to the top of its travel. The latch release button 80 is depressed, shifting the vertical position link 87 over the track 20 and the latch 72 out of the notch 73. Once the latch 70 has been pivoted sufficiently to come out of the notch 73, rearward pressure on the spot filmer will shift it rearwardly until the latch 70 engages the latch bumper 76 and pivots into engagement with the park notch 72.

The rearward shifting of the spot filmer and the natural action as the parking is acheived, shifts the carriage downwardly enough that the vertical link 87 moves into engagement with the top of the track 20 and will remain there once the button is released until action is taken to shift the spot filmer out of the park position. Moreover, even if the latch 87 should be brought forward by the action of the spring 93 once the spot filmer is in its parked position, substantially no downward movement is obtainable because the spot filmer is over the top of the mast 18 and will rest against it.

Another outstanding feature of the latch release structure is that it prevents movement of the spot filmer rearwardly from its operating position unless the spot filmer has been moved to the top of its travel. To accomplish this, the vertical link 87 is positioned such that it will strike the front of the track 20 if the button 80 is depressed at a time when the spot filmer is not raised to a point when it can pivot over the top of the track 20. The lost motion connections 89, 90, the depth of the groove 74 and the size of the latch 70 are such that the latch 70 cannot be pivoted about its pivot 71 a sufficient amount to come out of the notch 73 until the vertical link 87 is able to move over the top of the track 20. Thus, one cannot accidentally shift the spot filmer out of its operating position until the spot filmer carriage has been moved substantially to the top of its permissible travel.

The spot filmer of this invention is preferably used in conjunction with automatic X-ray shutter control which will be described in an application to be filed by E. A. Norgren. A portion of that automatic shutter control is shown in FIGS. 3 and 5.

A shutter-control bracket 100 is mounted in the last 18. The shutter-control bracket 100 supports a guide rod 101. A position control member 102 is provided which has upper and lower apertured flanges 103. The guide rod 101 projects through the apertures in the flanges 103.

The position-control member 102 is, in the embodiment shown, connected by a connecting portion 104 to the intermediate carriage 33. As the intermediate carriage 33 moves up and down, the position-control member moves up and down with it. The position-control member is guided along a rectilinear path by the guide rod 101.

The position-control member 102 carries a pair of rollers 105. A rheostat control shaft 106 is journaled on the shutter-control bracket 100 and engaged by the rollers 105. The control shaft 106 is rectangular in cross-section and of a longitudinally twisted or spiral configuration. As the position-control member 102 moves up and down with the intermediate carriage 33, the control rollers 105 engage the surface of the control shaft 106, causing it to rotate.

Rotation of the control shaft 106 causes rotation of the rotatable contactors of a pair of "pots" or variable rheostats 107. The rheostats are connected into the shutter control circuit so that rotation of them causes automatic compensation in that circuit for the position of the spot filmer.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

Claims

What is claimed is:

1. An X-ray apparatus, comprising:

a. a table having a tiltable body;

b. a tower movably carried on said body;

c. a mast forming part of said tower and supporting a mechanism for contributing to the production of an X-ray image for movement along a mechanism path toward and away from said body between mechanism extended and mechanism storage positions, said mechanism extended position being nearer said table body than said mechanism storage position;

d. counterweight structure forming part of said tower and being movable along a structure path which is substantially parallel to said imaging path between structure extended and structure storage positions;

e. coupling means coupling said mechanism and said structure for moving said structure along said structure path a certain distance in response to movement of said mechanism along said mechanism path a lesser distance, said coupling means being operable to position said structure in said structure extended position when said mechanism is in said mechanism extended position, and being operative to position said structure in said structure storage position when said mechanism is in said mechanism storage position;

f. said mechanism being movable, when in said mechanism storage position, along a parking path which intersects said structure path to position said mechanism in a parked position;

g. said coupling means being operative to move said structure across said parking path when said mechanism moves from said mechanism storage position to said mechanism extended position; and,

h. said coupling means being operative to prevent collision between said mechanism and said structure when said mechanism is moved along said parking path.

2. The apparatus of claim 1 additionally including means prohibiting the movement of said mechanism in directions toward and away from said structure path except when said mechanism is in said mechanism storage position.

3. An X-ray apparatus comprising:

a. an X-ray table having a top tiltable from the horizontal position to another position and return;

b. a column mounted in the table for movement relative to the table top;

c. said column including a vertical mast;

d. an imaging carriage device mounted on the mast for reciprocation toward and away from the table top;

e. an imaging device mounted on the carriage device and reciprocal relative to the carriage device from an operating position forward of the mast to a park position above the mast;

f. an intermediate carriage journaled within the mast for vertical movement relative thereto;

g. a counterweight assembly journaled on the intermediate carriage and movable relative thereto;

h. a pulley and cable system interconnecting the devices and the intermediate carriage and the intermediate carriage and the counterweight assembly respectively;

i. said counterweight assembly having a top position projecting above said mast and a lower park position within the mast; and,

j. said devices being coupled to a latching means maintaining said image device in its forward operating position at all times other than when the carriage device is raised to a height where the imaging device can pass over the mast assembly when shifted rearwardly and said latch means is released.

4. The apparatus of claim 3 wherein said latch means comprises:

a. a track on one of the devices and journaled for reciprocal movement on the other of the devices;

b. a latching mechanism carried by the other of the devices and including a latch pivotally mounted thereon;

c. said truck including park and operating position notches;

d. said latch being selectively engageable with the notches one at a time;

e. latch release means connected to the latch and actuatable to pivot the latch out of engagement with a selected one of said notches; and,

f. vertical position maintenance means carried by a selected one of the mast and the devices, said maintenance means being selectively positionable between a first of said devices and said mast to maintain said devices in an elevated position when the imaging device is in its park position and to prevent movement of the imaging device from its operating position to its park position until the imaging carriage is adequately elevated for parking movement.

5. In an X-ray apparatus having a table having a pedestal, a body tiltably mounted on the pedestal for tilting from a horizontal to a vertical position, and a tower assembly movably carried by the body and including a mast supporting said imaging device for movement toward and away from the table body, the improvement comprising:

a. an intermediate carriage movably carried by the mast;

b. a counterweight assembly movably carried by the mast; and,

c. counterweight coupling means coupling the imaging device, the counterweight assembly and the intermeidate carriage together such that on movement of the imaging device a given distance the intermediate carriage will move a certain distance in a direction opposite the imaging device and the counterweight assembly will move a greater distance than the imaging device thereby providing a mechanical advantage to the counterweight.

6. The apparatus of claim 5 wherein the counterweight assembly comprises a counterweight carriage journaled on the intermediate carriage for vertical reciprocal movement relative thereto and counterweights mounted on said counterweight carriage.

7. The apparatus of claim 6 wherein the counterweight coupling means comprises pulley and cable systems respectively connecting the intermediate carriage to the imaging device and the counterweight assembly to the intermediate carriage and arranged such that the counterweight assembly moves substantially twice said given distance on movement of the imaging device.

8. The device of claim 5 wherein the intermediate carriage and the counterweight assembly have extended positions wherein both extend above the top of the mast and wherein said intermediate carriage and counterweight assembly are maintained in said extended position by the coupling means when said imaging device is in its lowermost position.

9. In an X-ray apparatus including an imaging device carriage mounted on a mast and movable reciprocally on mast tracks and an imaging device having tracks mounted on the carriage for reciprocal movement therealong in a path generally normal to the path of carriage movement on said mast, an improved latching mechanism comprising:

a. one of said image device tracks including spaced park and operating position notches;

b. a latch pivotally mounted on said carriage and selectively engageable with said notches one at a time;

c. manually actuatable linkage connected to said latch for selectively pivoting said latch out of engagement with each of said notches;

d. resilient means biasing said latch into said notches selectively and one at a time whenever said linkage is released and the latch is aligned with one of the notches;

e. a vertical position maintenance link pivotally mounted on said carriage;

f. a lost motion connection between said vertical link and said latch; and,

g. said vertical link being positioned such that when the carriage is substantially in its uppermost position actuation of the manually actuatable linkage will pivot the vertical link over the top of one of said mast tracks and the latch will come out of the operating position notch but when the imaging device is in an operating position and the carriage is not sufficiently elevated, the link will strike the mast track and prevent disengagement of the latch with the operating position notch.

10. The apparatus of claim 9 wherein a second resilient means biases said vertical link from its park position over said one mast track.

11. In an X-ray apparatus including a table having a pedestal, a body tiltably mounted on the pedestal for tilting from a horizontal to a vertical position, and a tower assembly movably carried by the body, the tower assembly including a mast supporting an imaging device for movement toward and away from the table body, the improvement comprising:

a. a counterweight assembly forming part of the tower assembly, the counterweight assembly being mounted on the mast and movable relative thereto;

b. counterweight coupling means coupling the imaging device to the counterweight assembly such that on movement of the imaging device a given distance the counterweight assembly will move a greater distance than the imaging device thereby providing a mechanical advantage;

c. parking means coupling the imaging device to the remainder of the tower assembly and permitting selective rectilinear movement of the imaging device rearwardly from an operating position forward of the mast to a park position over the top of said counterweight assembly;

d. said tower assembly including an imaging device carriage reciprocally mounted on the mast and carrying said image device;

e. latch means to lock the imaging device selectively in the operating position or in the park position; and,

f. the latch means including a means to maintain the carriage in its fully-elevated position and preventing the movement of the imaging device from the operating position to the park position whenever the imaging device carriage is below its park position.

12. In an X-ray apparatus including a carriage device reciprocally mounted on a mast for movement toward and away from an X-ray table, and an imaging device reciprocally mounted on the carriage device for movement along a rectilinear path paralleling the table top from an operating position to a park position, a latching structure comprising:

a. a track on one of the devices and journaled for reciprocal movement on the other of the devices;

b. a latching mechanism carried by the other of the devices and including a latch pivotally mounted thereon;

c. said track including park and operating position notches;

d. said latch being selectively engageable with said notches one at a time;

e. latch release means connected to the latch and actuatable to pivot the latch out of engagement with a selected one of said notches; and,

f. vertical position maintenance means carried by a selected one of the mast and the devices, said maintenance means being selectively positionable between a first of said devices and said mast to maintain said devices in an elevated position when the imaging device is in its park position and to prevent movement of the imaging device from its operating position to its park position until the imaging carriage is adequately elevated for parking movement.

13. The apparatus of claim 12 wherein the position maintenance means is carried by one of the devices and engageable with a track on the mast.

14. The apparatus of claim 12 wherein there is a lost motion connection between the latch and the position maintenance means.

15. In an X-ray apparatus including a table having a pedestal, a body tiltably mounted on the pedestal for tilting from a horizontal to a vertical position, and a tower assembly movably carried by the body, the improvement comprising:

a. said tower assembly including a mast subassembly supporting an imaging device for movement longitudinal of the tower assembly toward and away from the table body;

b. a counterweight subassembly forming part of the tower assembly, the counterweight subassembly being carried by the mast subassembly and movable relative thereto;

c. counterweight coupling means coupling the imaging device to the counterweight subassembly such that on movement of the imaging device a given distance the counterweight subassembly will move a certain distance;

d. said subassemblies having a storage position and an extended position, the combined dimension of the subassemblies longitudinally of the tower being greater when in the extended position than when in the storage position; and,

e. parking means coupling the imaging device to the remainder of the tower assembly and permitting selective rectilinear movement of the imaging device rearwardly from an operating position forward of the mast subassembly to a park position over the subassemblies when they are in the storage position.

16. The apparatus of claim 15 wherein the counterweight subassembly is telescopically carried by the mast subassembly.

17. The apparatus of claim 16 wherein a counterweight subassembly is fully within the mast subassembly within said storage position and projects outwardly of the mast subassembly when in said extended position.

18. The apparatus of claim 15 wherein said certain distance is greater than said given distance thereby providing a mechanical advantage.

19. The apparatus of claim 15 wherein the image device is movable to its park position only when it is substantially at its maximum distance from the table body.

20. The apparatus of claim 19 wherein a latch means is interposed between the imaging device and the remainder of the tower assembly to prevent such movement to the park position until the image device is at such maximum position.

21. The apparatus of claim 19 wherein a means prevents movement of the imaging device toward the table body when the imaging device is in its park position.

22. The apparatus of claim 15 wherein the counterweight subassembly includes a counterweight carriage and an intermediate carriage.

23. The apparatus of claim 22 wherein the counterweight carriage and the intermediate carriage are movable relative to one another and relative to the mast subassembly.

24. The apparatus of claim 23 wherein the counterweight carriage projects from the intermediate carriage and both carriages project from the mast subassembly when in said extended position.

25. In an X-ray apparatus including a table having a pedestal, a body tiltably mounted on the pedestal for tilting from a horizontal to a vertical position, and a tower assembly movably carried by the body, the tower assembly including a mast supporting an imaging device for movement toward and away from the table body, the improvement comprising:

a. a counterweight assembly forming part of the tower assembly, the counterweight assembly being mounted on the mast and movable relative thereto;

b. counterweight coupling means coupling the imaging device to the counterweight assembly such that on movement of the imaging device a given distance the counterweight assembly will move a greater distance than the imaging device thereby providing a mechanical advantage;

c. parking means coupling the imaging device to the remainder of the tower assembly and permitting selective rectilinear movement of the imaging device rearwardly from an operating position forward of the mast to a park position over the top of said counterweight assembly;

d. the counterweight assembly being movable to an extended position projecting above the top of the mast; and,

e. the imaging device being in its lowermost position when the coupling means maintains the counterweight assembly in its extended position.

26. An X-ray apparatus, comprising:

a. a table having a body tiltable between horizontal and vertical positions;

b. a tower movably carried on said body;

c. a counterweight subassembly forming part of said tower and being movable longitudinally of said tower along a first path between counterweight extended and counterweight storage positions;

d. a mast subassembly forming a part of said tower and supporting an imaging device for movement longitudinally of said tower along a second path substantially parallel to said first path between device extended and device storage positions, said device extended position being nearer said table body than said device storage position;

e. coupling means coupling said imaging device and said counterweight subassembly for moving said counterweight assembly along said first path a certain distance in response to movement of said imaging device along said second path a lesser distance, said coupling means being operable to position said counterweight subassembly in said counterweight extended position when said imaging device is in said device extended position, and being operative to position said counterweight subassembly in said counterweight storage position when said imaging device is in said device storage position;

f. said imaging device being movable, when in said device storage position, along a parking path which intersects said first path to position said imaging device in a parked position along said first path;

g. said counterweight storage position being sufficiently removed from said parked position to prevent collision between said imaging device and said counterweight subassembly when said imaging device is moved along said parking path; and,

h. said coupling means being operative to move said counterweight subassembly across said parking path when said imaging device moves from said device storage position to said device extended position.

27. The apparatus of claim 26 additionally including parking means prohibiting the movement of said imaging device along said parking path except when said imaging device is in said device storage position.

28. The apparatus of claim 27 wherein said parking means includes an acutator button which is operable when said imaging device is in said device storage position to permit the movement of said imaging device along said parking path, and control means for preventing the operation of said actuator button when said imaging device is removed from said device storage position.

29. The apparatus of claim 26 wherein said counterweight subassembly is positioned across said parking path when said imaging device is in said device extended position.

30. The apparatus of claim 29 wherein said coupling means includes cable means interconnecting said counterweight subassembly and said imaging device for moving said counterweight subassembly along said first path in a direction opposite to the movement of said imaging device along said second path in response to movement of said imaging device along said second path, whereby said counterweight subassembly moves toward said table body from said counterweight extended position when said imaging device moves away from said table body from said device extended position.

31. The apparatus of claim 30 wherein said coupling means is operable to move said counterweight subassembly along said first path through approximately twice a given distance in response to movement of said imaging device along said second path through said given distance.