Personnel/load Carrying System

Abstract

An apparatus system for moving personnel and/or other loads from one elevation point to another. The apparatus system includes a carrier traversing an inclined carrying line secured between higher and lower elevation points, a movable counterweight for counterbalancing weight of the carrier, a cable interconnecting the carrier and counterweight, sheaves coacting with the cable, and fluid power means for adjusting rate and direction of movement of the carrier along the carrying line, the carrier being automatically returnable to the upper elevation point if desired. Braking means are provided to stop the carrier in an emergency situation.

Description

BACKGROUND OF THE INVENTION

Numerous types of construction projects as well as drilling rigs of the derrick type for drilling oil and gas wells require the transporting of personnel and other loads to and from elevated levels. Stairs, elevators and the like that are ordinarily used result in wasted time and motion. Particularly in the drilling of oil and gas wells is there danger of blowouts, explosions, fires and other perils necessitating quick evacuation from working structures. Consequently, it would be advantageous to provide a means of descent from these types of structures that is reliable, safe and fast as well as having the capability of moving loads from one elevation to another with controls stationed at either level. The present invention is directed to such means.

An example of one form of a device for carrying personnel from one level to another is illustrated in my pending United States patent application Ser. No. 239,137 filed Mar. 29, 1972 for a "Descension Device." Other forms of devices for moving personnel are illustrated in references cited in the file of such application.

Applicant presently is aware of existing patents in the field of art including U.S. Pat. Nos. 864,405 (Bowen, 1907); 1,556,555 (Brown, 1925); 1,571,096 (Rambin et al., 1926); 1,615,657 (Schwafel, 1927); 1,684,251 (Thomas, 1928); 1,888,911 (Graffenreid, 1932); 2,321,248 (Rose et al., 1943); 2,670,890 (Hodge, 1954); 2,948,348 (Bott, 1960); and the references cited therein.

SUMMARY OF THE PRESENT INVENTION

The apparatus system of the present invention generally provides means for moving personnel and/or other loads between higher and lower elevations and comprises a carrying line inclined from and anchored between the higher and lower elevation points, carrier means for traversing the carrying line to support the personnel or load being moved, movable counterweight means for counterbalancing weight of the carrier means, cable and sheave means inter-connecting and providing coaction between the carrier means and the counterweight means, and fluid power means for adjusting rate and direction of movement of the carrier means along the carrying line. Preferably, the apparatus system also includes braking means secured to the carrier means and coacting with the carrying line and the cable and sheave means such that slacking or severance of the cable and sheave means engages the braking means with the carrying line to bring the carrier means to a stationary position with respect to the carrying line. The fluid power means regulates movement of the counterweight means for purposes both of descending and ascending operation of the carrier means.

It is, therefore, an object of the present invention to provide a personnel/load moving device providing a means of quick movement of the personnel/load between higher and lower elevation points through manipulation or operation of fluid power means.

Another object of the present invention is to provide such a personnel/load moving device having automatically operable braking means to bring the carrier portion of the device to a halt upon slaking, severance or failure of the supporting cable insuring safety of the personnel or other load.

A still further object of the present invention is the provision of a descension device providing a means of quick descent from higher to lower elevation points in emergency situations, the carrier portion of the device moving personnel away from the work area rather than down alongside of the work area.

Still another object of the present invention is the provision of a personnel/load carrying system having fluid power means for adjusting rate and direction of movement of the carrier portion of the system along a carrying line, the fluid being pressurized to lift the personnel/load, the pressure of the fluid being reduced or otherwise released to lower the personnel/load.

Other and further objects, features and advantages will be apparent from the following description of preferred embodiments of the invention, given for the purpose of disclosure and taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

In the drawings forming a part of the disclosure herein, like character references designate like parts throughout the several views, wherein,

FIG. 1 is a side elevation view of the personnel/load moving apparatus system according to the present invention,

FIG. 2 is a partial elevation view, partly in cross section, taken along the line 2--2 of FIG. 1, showing the higher elevation end of the carrying line, and showing the cable and sheave means as well as the fluid power means for adjusting rate and direction of movement of the carrier portion of the system,

FIG. 3 is a partial elevation view showing the carrier means latched by means of a retention device at the lower elevation point,

FIG. 3A is a partial elevation view of the cable and sheave means as well as the fluid power means with a schematic of means for adjustably pressuring and directing flow of the fluid, and

FIG. 4 is a partial elevation view of the carrier with associated braking means.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Shown in FIG. 1 is a derrick 10 typical of that used in the drilling of oil and gas wells. While the apparatus system of the present invention will be described with respect to a derrick, it will be understood that the invention may be used in any application requiring movement of personnel and/or other loads to and from elevated points. The apparatus system of the present invention is particularly useful in situations wherein it is desired to move the personnel and/or other load outward, below and away from the work site so as not to be subjected to perils that might arise in the work area.

A carrying line 12 is inclined from and anchored between higher and lower elevation points. For example, the upper end of the line 12 may be anchored to the derrick 10 by suitable supports. Similarly, the lower end of the line 12 may be attached or anchored to beams 16 or other support members.

Continuing with respect to FIG. 1, carrier means 18 are provided for traversing the carrying line 12 to support the personnel or other load being moved along the line. The carrier means 18 generally includes a gondola 20 suspended from a frame 22, details of the carrier means being explained with more specificity hereafter with respect to FIGS. 3 and 4. The carrier means 18 is also illustrated in dotted outline in FIG. 1 in an intermediate position with respect to the carrying line 12 as well as at the lower elevation point or ground level.

Shown in FIG. 1 and as will be explained hereafter in more detail with respect to FIGS. 2 and 3A, a cable 24 interconnects the carrier means 18 and the movable counterweight means 26. The cable 24 engages sheaves 28 and 30 and engagably coacts with two opposed sets of sheaves 36 and 38 shown in FIG. 2.

Further shown in FIG. 1 is a fluid power means 32 for adjusting rate and direction of movement of the cable 24 and in turn the carrier means 18 with respect to the carrying line 12.

With respect now to FIG. 2, the cable 24 engages and coacts with two opposed sets of sheaves, the number of sheaves in each set being proportional to the ratio desired of movement of the counterweight 26 relative to traverse of the carrier means 18. As shown in FIG. 2, one set 36 of the sheaves comprises two sheaves and the other set 38 comprises three sheaves. It will be understood and recognized by those skilled in the art, however, that the number of sheaves in each set may be varied as desired.

From the sheaves 36 and 38, the end of the cable 24 is anchored and secured either to the counterweight 26 or to another suitable support such as a cable anchor member 40.

The fluid power means for adjusting rate and direction of movement of the carrier means 18 along the carrying line 12 is illustrated in FIG. 2. An enclosed tubular member 42 is provided at its upper end with a suitable stuffing box 44 for slidably and sealably receiving a cable 46 passing into the upper end of the tubular member 42. One end of the cable 46 is secured by an anchor member 48 to the counterweight 26 and at its other end to a piston member 50 slidable within the tubular member 42. Mounted on the piston 50 at either end are suitable seals 52 that prevent flow of fluid between the piston 50 and the inner wall of the tubular member 42. As shown in the drawing, the cable 46 engages and is supported by an upper sheave 54 and a lower sheave 56, both sheaves being supported on beams or other suitable framework as shown in the drawing.

A fluid reservoir 58 is mounted in spaced relation from and parallel to the tubular member 42. The reservoir 58 is preferably an upstanding tubular member which together with the tubular member 42 provide tracks on which recessed rollers 60 may move. The rollers 60 are journalled to the counterweight 26 and form a part thereof whereby the counterweight 26 may move in a vertical plane as indicated by the arrow 62.

The fluid reservoir 58 stores fluid for use in moving the piston 50 to operate the system of the present invention. The preferred fluid is air although hydraulic or other suitable fluids may be used. Air is supplied such as by means of a conduit 64 and is pressurized such as by means of a compressor, not shown. Of course, if hydraulic fluid is the fluid used, a pump in the line 64 may be provided for pressurization of the fluid.

A conduit or pipe 66 provides communication for the fluid with the interior of the tubular member 42 whereby pressure of the fluid may act against the upper end of the piston 50. Provided in the air line 66 is a three-way valve 68 that preferably is actuated by a suitable solenoid 70, one leg 72 of the three-way valve 68 venting to the atmosphere preferably through an adjustable orifice 74. It will be appreciated, of course, that the three-way valve 68 and solenoid 70 may be integrated. While not absolutely necessary, other accessories may be provided in the line 66 such as a control valve 76, a lubricator 78, and a pressure regulator 80. Thus, air may pass through the conduit 66 into the three-way valve 68 (when the valve 68 is moved counterclockwise 90.degree. from the position shown in FIG. 2), and thence into the tubular member 42. Preferably, the three-way valve 68 is actuated by the solenoid 70 which in turn in manually controlled by means of a suitable switch 82 that may be mounted at the lower elevation point as shown in FIG. 1. Thus, the fluid power means 32 may be controlled from the lower elevation point to in turn control movement of the carrier means 18.

Continuing with respect to FIG. 2, a suitable compression spring 84 is secured to a face plate 86 mounted at the upper end of the carrying line 12. Mounted on the face plate 86 is a limit switch 88 having an extended actuator 90 to engage the frame 22 of the carrier means 18. Thus, when a person is ascending on the carrier means 18 and approaches the upper end of the carrying line 12, the frame 22 engages the compression spring 84 and upward movement of the carrier is terminated. When the person steps off of the carrier means 18, fluid pressure within the tubular member 42 continues to act against the piston 50 which in turn urges the frame 22 of the carrier means 18 upward against the compression spring. With the load removed from the carrier means 18, the fluid pressure is sufficient to cause the frame 22 of the carrier means 18 to further compress the spring 84 so that the frame 22 engages the actuator 90 of the limit switch 88. Actuation of the limit switch 88 then causes the solenoid 70 to close the three-way switch 68, i.e. move the switch 68 to position shown in FIG. 2. The carrier means 18 will remain in position at the upper elevation point as shown in FIG. 2 provided the weight of the counterweight means 26 is substantially the same as that of the carrier means 18.

Referring now to FIGS. 3 and 4, the frame 22 of the carrier means 18 is provided with an upper grooved roller 92 and a lower grooved roller 94, both rollers being journalled to the frame 22. The rollers 92 and 94 engage over the carrying line 12 whereby the frame 22 may traverse the carrying line. The gondola 20 (as shown in FIG. 1) is suspended from the frame 22 such as by means of a suspension arm 96 suitably secured to the frame and gondola.

Braking means are mounted on the carrier means 18. The brake system includes a control lever 98 suitably secured to the frame 22 and the upper end of which is fastened to the cable 24. As shown in FIGS. 3 and 4, the control lever 98 is journalled by means of a pin 100 to structural supports 102 and 104, the structural supports being secured to the frame member 22 such as by welding, bolting or other suitable means. Fastened to the structural supports 102 is a suitable stop member 106 which serves to limit upward movement of the control lever 98 as the control lever pivots on the pin 100. Thus, when the pulling force is exerted on the control lever 98 by the cable 24, the lever 98 engages the stop 106 whereby the carrier means 18 is moved upward.

Secured to the lower end of the control lever 98 is a friction plate 108 in juxtaposition to the carrying line 12. A matching friction plate or brake table 110 is secured to the frame 22 under the carrying line 12 so that engagement of the friction plate 108 with the carrying line 12 binds the carrying line 12 between the friction plate 108 and table 110 to stop movement of the carrying means 18. If for any reason the cable 24 slackens or severs, a spring 112 secured at one end to the frame 22 and at the other end to the lower end of the control lever 98 causes the friction plate 108 to engage with the carrying line 12. It will be understood, of course, that the spring 112 should be of such size and modulus as to release the friction plate 108 from the carrying line 12 when the cable 24 is taut yet biases the friction plate toward the carrying line and into intimate contact therewith upon slacking or severance of the cable 24.

As shown in FIGS. 3 and 4, a brake lever arm 113 is provided for manual control of the braking system, if desired. One end of the brake lever arm 113 is rigidly secured to the lower end of the control lever 98. Thus the other end of the arm 113 may be pulled manually to force the friction plate 108 into the braking position.

Continuing with respect to FIGS. 3 and 4, a latch 114 provides means for releasably retaining the carrier means 18 as close as possible to the lower elevation point, i.e., adjacent the lower carrying line supports 16. Otherwise, action of the springs 132, 134 and 136 might cause the carrier means 18 to lift slightly thereby causing some inconvenience in boarding the gondola 20. The latch 14 is journalled such as by a pin 116 to an extension 118 of the carrier means frame 22. Also forming a part of the latch is a handle 120 acting as a lever arm and integrally secured to the latch body 114 rearward of the pin 116. As best shown in FIG. 3, a spring 122 urges the handle 120 upward thereby urging the head of the latch 114 downward and into engagement with a catch 124 secured to the carrying line 12. Both the latch 114 and the catch 124 have angled faces to promote sliding and snapping engagement of the latch with the catch as the carrier means 18 moves downwardly. When it is desired to begin an ascent with the carrier means 18, the handle 120 is pulled downward thereby releasing the latch 114 from the catch 124.

Operation of the system of apparatus according to the present invention will be explained first with respect to descent from higher to lower elevation points by means of the present invention. Thus, for example, if a person or other load is located on the platform 130 adjacent the higher elevation point of the carrying cable 12, the person steps into the gondola 20 shown in FIG. 1. The three-way valve 68 is manually or by remote control moved to the position shown in FIG. 2. The adjustable orifice or valve 74 is maintained in a suitable open position to control the rate of flow therethrough. Consequently, air or fluid pressure within the tubular member 42 is released at a controlled rate and the piston 50 within the tubular member 42 may move upward. Weight of the person or other load in the carrier means 18 exerts a force on the cable 24 which in turn pulls the counterweight 26 and piston 50 upward. As will now become apparent, the adjustable orifice or valve 74 is opened only in proportion to the rate of descent desired. As the person or other load descends on the carrier means 18, the piston 50 arises within the tubular member 42 pushing air or fluid ahead and out through the three-way valve leg 72. The adjustable orifice or valve 74 restricts the flow of fluid as desired thereby controlling rate of descent of the carrier means 18. As the carrier means 18 approaches the lower elevation point as shown in dotted outline in FIG. 1, the latch 114 engages the catch 124 of the retention means as shown in FIG. 3. Thus, after the person steps out of the gondola 20 or the load is otherwise removed from the carrier means 18, the carrier means remains at the lower elevation point for use in an ascent.

Preferably weight of the counterweight means 26 is at least as great as weight of the carrier means 18. Depending on the results desired, the counterweight 26 may be constructed so as to be slightly heavier than weight of the carrier means 18 so that the carrier means 18 may return automatically to the higher elevation point upon release of the latch member 114 from the catch 124. Of course, a suitable vent preferably should be provided on the lower end of the tubular member 42 so that no back pressure is created against the piston 50 in such an operation.

Preferably provided within the tubular member 42 is a suitable compression spring 132 as shown in FIG. 2 surrounding the cable 46 to cushion and slow movement of the piston 50 as it approaches the top of the tubular member during descending operation of the carrier means 18. Similarly, suitable compression springs 134 and 136 preferably are secured to a cross beam 138 to engage spring receptacles 140 mounted on the counterweight 26. Thus, as shown in FIG. 3A, the springs 134 and 136 compress upon engagement with the counterweight 26, thereby slowing and cushioning movement of the counterweight as it approaches the uppermost position. Cushioning effect of each of these springs thereby promotes comfort and safety of the descending operation of the carrier means 18.

With respect to operation of the system in an ascent, a person steps onto the gondola 20 (or a load is placed thereon) of the carrier means 18 as shown in FIG. 1 and the handle 120 of the retention means is actuated to release the latch 114 from the catch 124 as shown in dotted outline in FIG. 3. Then the switch 82 is actuated to in turn actuate the solenoid 70 to move the three-way valve 68 from the position shown in FIG. 2 to the position shown in FIG. 3A. With the three-way valve 68 in the position shown in FIG. 3A, air or other fluid pressure within the pressurized fluid reservoir 58 is transmitted by means of the line 66 through the valve 68 and into the tubular member 42. The pressure should be great enough to force the piston 50 downward in the tubular member 42 thereby pulling the counterweight 26 downward and in turn lifting the carrier means 18. When the carrier means reaches the higher elevation point as shown in FIG. 1, the person may step from the gondola 20 onto the platform 130 or the load on the gondola may be removed. Upon removal of such load or weight from the gondola 20, continued exertion of air or fluid pressure against the piston 50 causes the carrier means 18 to move slightly higher to compress the spring 84 as shown in FIG. 2. The frame 22 of the carrier means then contacts and actuates the limit switch 88 to in turn actuate the solenoid 70 thereby moving the three-way valve 68 to the position shown in FIG. 2. Provided the counterweight means 26 is substantially the same weight as the carrier means 18, the carrier means 18 will remain at the upper elevation point even though air or fluid is vented from the tubular member 42. Thus, the carrier means 18 remains in the upper position ready for reuse as necessary.

As an alternative to the fluid system illustrated in the drawings and described herein, a system similar to that disclosed in my pending application Ser. No. 239,127 previously identified may be used. Such other system is particular useful if hydraulic fluid is employed in view of the closed nature of the piping circuitry.

As will now be appreciated, the number of sheaves in the two sets of sheaves 36 and 38, respectively, may be varied according to the overall size of apparatus employed, space available for travel of the counterweight means 26, and length of traverse of the carrier means 18 along the carrying line 12. In light of the disclosure herein, it will be well within the ability of one skilled in the art to select the desired sheave means.

Thus provided is a system of apparatus for moving personnel or other loads from one elevation to another. The system may be used not only as a means for emergency escape from an elevated point out and away from a work area, but also may be used as a means of transporting personnel and other loads under regular utility conditions. The brake system associated with the carrier means insures safety of personnel using the apparatus should the motive cable 24 malfunction in any way.

The present invention, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned as well as others inherent therein. While a presently preferred embodiment of the invention has been given for the purpose of disclosure, numerous changes in the detail of construction and the combination, shape, size and 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. A system for moving a load between higher and lower elevations, comprising:

a. a carrying line inclined from and anchored between the higher and lower elevation points,

b. carrier means for traversing the carrying line (a) to support the load being moved,

c. movable counterweight means for counterbalancing weight of the carrier means (b),

d. cable and sheave means interconnecting and providing coaction between the carrier means (b) and the counterweight means (c), and

e. fluid power means for adjusting rate and direction of movement of the carrier means (b) along the carrying line (a) , said fluid power means including,

i. an upstanding, enclosed tubular member provided at its upper end with a stuffing box means for slidably and sealably receiving a cable passing into the upper end of said tubular member,

ii. a piston member slidable within the tubular member (e) (i),

iii. a cable interconnecting the counterweight means (c) and the piston (e) (ii),

iv. sheave means coacting with the cable (e) (iii) for guiding said cable,

v. fluid contained within the tubular member (e) (i), and

vi. means for adjustably pressuring and directing flow of the fluid (e) (v).

2. The system of claim 1 wherein the means (e) (vi) for adjustably pressuring and directing flow of the fluid (e) (v) includes, more specifically,

aa. a pressurized fluid reservoir for the fluid,

bb. a conduit providing fluid communication between the fluid reservoir (aa) and the tubular member (e) (i), and

cc. valve means in the conduit (bb) for controlling pressure and direction of flow of fluid in said conduit (bb).

3. The system of claim 1 wherein the cable and sheave means includes, more specifically,

i. a cable, one end of which engages the counterweight means (c) and the ther end of which is secured to the carrier means (b), and

ii. two opposed sets of sheaves coacting with the cable (b) (ii), the number of sheaves in each set being proportional to the ratio desired of movement of the counterweight means (c) relative to traverse of the carrier means (b).

4. The system of claim 1 including, additionally,

f. braking means mounted on the carrier means (b) coacting with the carrying line (a) and the cable and sheave means (b) such that slackening or severance of the cable and sheave means (b) causes engagement of the braking means with the carrying line (a) to bring the carrier means (b) to a stationary position with respect to the carrying line (a), said braking means including,

i. a control lever journalled to the carrier means (b) so as to pivot in the vertical plane, the control lever serving to secure the cable means of the cable and sheave means (b) to the carrier means (b) by attachment of said cable means to one end of the control lever,

ii. a friction plate secured to the other end of the control lever (f) (i) in juxtaposition to the carrying line (a), and

iii. spring means secured between the carrier means (b) and the control lever (f) (i) so as to bias the friction plate (f) (ii) toward the carrying line (a) and into intimate contact therewith upon slacking or severance of the cable means (d).

5. The system of claim 5 including, additionally, a brake lever arm, one end of which is rigidly secured to control lever (f) (i) for manual operation of the braking means (f).

6. The system of claim 2 wherein, more particularly, the valve means (e) (vi) (cc) is a three-way valve.

7. The system of claim 3 wherein in the two opposed sets of sheaves (d) (ii), one set comprises two sheaves and the other set comprises three sheaves.

8. The system of claim 2 wherein, more particularly, the pressured fluid reservoir (e) (vi) (aa) comprises an upstanding tubular member oriented parallel to the tubular member (e) (ii), and the movable counterweight means (c) comprises a weight member supported on rollers between and for movement along both said tubular members.

9. A system for moving a load between higher and lower elevations, comprising,

a. a carrying line inclined from and anchored between the higher and lower elevation point,

b. a carrier having rollers for engaging and traversing the carrying line (a) to support the load being moved,

c. movable counterweight means at least as heavy as the carrier (b) for counterbalancing weight of the carrier means (b),

d. a cable connected at one end to the carrier (b) and at the other end engaging the movable counterweight means (c),

e. two opposed sets of sheaves coacting with the cable (d), the number of sheaves in each set being proportional to the ratio desired of movement of the counterweight means (c) relative to traverse of the carrier (b), and

f. fluid power means for adjusting rate and direction of movement of the carrier (b) along the carrying line (a).

10. The system of claim 9 wherein the fluid power means (f) includes,

i. an upstanding, enclosed tubular member provided at its upper end with a stuffing box means for slidably and sealably receiving a cable passing into the upper end of said tubular member,

ii. a piston member slidable within the tubular member (f) (i),

iii. a cable interconnecting the counterweight means (c) and the piston member (f) (ii),

iv. sheave means coacting with the cable (f) (iii) for guiding said cable,

v. fluid contained within the tubular member (f) (i), and

vi. means for adjustably presuring and directing flow of the fluid (f) (v).

11. The system of claim 10 wherein the means (f) (vi) for adjustably pressuring and directing flow of the fluid (f) (v) includes, more specifically,

aa. a pressured fluid reservoir for the fluid,

bb. a conduit providing fluid communication between the fluid reservoir (aa) and the tubular member (f) (i), and

cc. valve means in the conduit (bb) for controlling pressure and direction of flow in said conduit (bb).

12. The system of claim 9 including, additionally,

g. braking means mounted on the carrier (b) and coacting with the carrying line (a) and the cable (d) such that slacking or severance of the cable (d) causes engagement of the braking means with the carrying line (a) to bring the carrier (b) to a stationary position with respect to the carrying line (a).

13. The system of claim 12 wherein, more particularly, the braking means (g) includes,

i. a control lever mounted on the carrier (b) so as to pivot in the vertical plane, the control lever serving to secure the cable (d) to the carrier (b) by attachment of said cable to one end of the control lever,

ii. a friction plate secured to the other end of the control lever (g) (i) in juxtaposition to the carrying line (a), and

iii. spring means secured between the carrier (b) and the control lever (g) (i) so as to bias the friction plate (g) (ii) toward the carrying line (a) and into intimate contact therewith upon slacking or severance of the cable (d).

14. The system of claim 13 including, additionally, a brake lever arm, one end of which is rigidly secured to the control lever (g) (i) for manual operation of the braking means (g).

15. The system of claim 9 including, additionally, means for releasably retaining the carrier (b) at the lower elevation point.

16. The system of claim 10 wherein, more particularly, the valve means (f) (vi) (cc) is a three-way valve.

17. The system of claim 9 wherein in the two opposed sets of sheaves (e), one set comprises two sheaves and the other comprises three sheaves.

18. The system of claim 11 wherein, more particularly, the pressured fluid reservoir (f) (vi) (aa) comprises an upstanding tubular member oriented parallel to the tubular member (e) (ii), and the movable counterweight means (c) comprises a weight member supported on rollers between and for movement along both said tubular members.

19. A system for moving a load between higher and lower elevations, comprising,

a. a carrying line inclined from and anchored between the higher and lower elevation points,

b. a carrier having rollers for engaging and traversing the carrying line (a) to support the load being moved,

c. movable counterweight means at least as heavy as the carrier (b) for counterbalancing weight of the carrier means (b),

d. a cable connected at one end to the carrier (b), the other end engaging the movable counterweight means (c),

e. two opposed sets of sheaves coacting with the cable (d), the number of sheaves in each set being proportional to the ratio desired of movement of the counterweight means (c) relative to traverse of the carrier (b),

f. fluid power means for adjusting rate and direction of movement of the carrier (b) along the carrying line (a), said fluid power means more particularly including,

i. an upstanding enclosed tubular member provided at its upper end with a stuffing box means for slidably and sealably receiving a cable passing into the upper end of said tubular member,

ii a piston member slidable within the tubular member (i),

iii. a cable interconnecting the counterweight means (c) and the piston (ii),

iv. sheave means coacting with the cable (iii) for guiding said cable,

v. fluid contained within the tubular member (i), and

vi. means for adjustably pressuring the fluid (v) including, more specifically,

aa. a pressured fluid reservoir,

bb. a conduit providing fluid communication between the fluid reservoir (aa) and the tubular member (i), and

cc. valve means in the conduit (bb) for controlling pressure and direction of flow of fluid in said conduit (bb), and

g. braking means mounted on the carrier (b) and coacting with the carrying line (a) and the cable (d) such that slacking or severance of the cable (d) causes the braking means to engage with the carrying line (a) to bring the carrier (b) to a stationary position with respect to the carrying line (a).

20. The system of claim 19, wherein, more particularly, the braking means (g) includes,

i. a control lever mounted on the carrier (b) so as to pivot in the vertical plane, the control lever serving to secure the cable (d) to the carrier (b) by attachment of said cable to one end of the control lever,

ii. a friction plate secured to the other end of the control lever (i) in juxtaposition to the carrying line (a), and

iii. spring means secured between the carrier (b) and the control lever (i) so as to bias the friction plate (ii) toward the carrying line (a) and into intimate contact therewith upon slacking or severance of the cable (b).