US3327999A

US3327999A - Rope locks

Info

Publication number: US3327999A
Application number: US527855A
Authority: US
Inventors: James D Mitchell
Original assignee: KNOXVILLE SCENIC STUDIOS Inc
Current assignee: KNOXVILLE SCENIC STUDIOS Inc
Priority date: 1966-02-16
Filing date: 1966-02-16
Publication date: 1967-06-27
Anticipated expiration: 1984-06-27

Description

June 27,1967 IMMT'WELL 3,327,999

ROPE LOCKS Filed Feb. 16, 1966 2 Sheets-Sheet 1 FIG. 2A

FIG.2C

5 INVENTOR. 2 v J. DONALD MITCHELL BY we .4 v

HIS ATTORNEY June 1967 J. D. MITCYHYELL ,3

- ROPE LOCKS Filed Feb. 16, 1966. 2 Sheets-Sheet 2 4 K K FIG4 INVENTOR. J; DONALD MITCHELL ms ATTORNEY United States Patent 3,327,999 ROPE LOCKS James 1). Mitchell, Knoxville, Tenn., assignor to Knoxville Scenic Studios, Inc., Knoxville, Tenn., a corporation of Tennessee Filed Fell. 16, 1966, Ser. No. 527,855 7 Claims. (Cl. 254-190) This invention pertains to an apparatus for controlling, braking or gripping ropes or cables, such devices being of the character described as rope locks.

It is known in the stagecraft art that rigging systems are used for suspending scenery, draperies, drops, curtains, lights and the like, the flown scenery, draperies, etc. usually beingsuspended from battens in the fly loft. Various types of rigging systems are used for flying scenery and the like. The older, the so-called rope system, still in use, has lines extending from the pipe batten or other unit which the lines are supporting, up throughv sheaves in an upper pulley, or head block, to a pin rail. In rope systems the pin rail is provided with belaying pins so that the lines can be tied oif. Using this rigging system, the stage hand, or flyman, must be careful to keep the ropes from getting mixed up on the fly floor causing flymen to trip or to lose control of their lines. In addition rope systems are slower than desired for modern productions, and they require much more physical effort than more modern systems.

Because of defects of older rope systems, quite often theaters are rigged with a combination of rope systems and counterweight systems, believing this to be the most flexible rigging system. However in many theaters variations of installations of counterweight systems are found. For instance in more elaborate systems additional supplemental riggings called spot blocks are employed for suspending equipment used for special effects.

In counterweight rigging, since scenery is frequently very heavy, the system includes counterweights so that less effort is required to raise and lower the units. In counterweight rigging systems, rather than being tied off individually, ropes or steel cables connected directly to scenery or to the batten or other unit, usually a substantial number, are connected to the top of a counterweight arbor in which Weights are placed. Each line passes from the batten through a loft block, and then through a head block to the top of the arbor. Ideally the weight of the object flown is exactly balanced by the weights in the counterweight arbor. Otherwise the system will be balanced so that the unit flown weighs a little more than the counter-' weights so that the flown unit is easy to control and the weights do not fall.

To raise and lower the counterweighted flown unit, a control rope, called a purchase line, is used. From the bottom of the counterweight arbor, a hemp, cotton or nylon control rope travels through a pulley on or near the floor, called a floor block, to an operatingstation, and

around through the head block to the top of the counterweight arbor where it is attached. Conventionally as many as three to nine purchase lines lead to each operating station where an operator or flyman raises and lowers the flown units. Often scenery or backdrops are changed during a production, particularly to bring them closer to the scene of action. This means that operators will have to be able rapidly to secure the purchase lines in place. This is accomplished by the use of a separate rope locking device for each purchase line, holding the scenery at any selected level. Hence, at each operating station the purchase line or control rope passes through a rope lock attached to a fixture, such as a locking rail, which is anchored to the stage floor or to a fly floor. There may be as many as fifty rope locks attached along a locking rail.

Oftentimes during events on the stage it is necessary 3,327,999- Patented June 27, 1967 to make quick changes in the scenery. Accordingly rope locks are necessary which can be rapidly operated. During such changes it may be necessary also to change the counterweights. In such instances misjudgements are sometimes made in the quality of counterweights to be loaded or unloaded from a system. In addition as a practical matter it is virtually impossible to achieve a perfectly balanced counterweighted system. This is especially true since stage hands in schools and small productions are usually inexperienced. An unbalanced system will cause no difliculty aslong as the purchase line is locked in place at the operating station. However, if the rope lock-v ing device is accidentally released, unbalanced heavy scenery or counterweights can come crashing down. The

Another object of the invention is the provision of a rope lock which cannot be easily unlocked by merely knocking or bumping into the handle thereof.

Still another object of this invention is that of providing a rope gripping device which can be very rapidly put into a locked position to effectively and positively grip and hold a purchase line.

A still further object of the invention is the provision of a rope lock which can be fabricated of steel rather than cast iron now extensively used.

In accordance with this invention these and such further objects as will be apparent to those skilled in the art, are accomplished by the provision of an improved rope lock of the type provided with a housing having openings in the top and bottom thereof permitting passage of a rope therethrough, and a gripping jaw within the housing adjacent its back end. The invention contemplates the combination of: a cam pivotally mounted within the housing adjacent its front end and having a handle extending upwardly therefrom outside the housing, the cam and handle operating as an eccentric lever as the handle is moved toward its vertical position, bringing about the com-" pression of the rope against the gripping jaw, clamping the. rope in a locked position when the handle is in a vertical position; with a locking key pivotally connected to the" cam at the base of the handle outside the housing. The locking key is so connected that it is free swinging under its own weight due to the action-of gravity, tending to stop in a vertical position. The locking key is so posi-j tioned that when the cam lever handle ismoved forward slightly past the vertical, the key comes to rest between the cam and a plate at the base of the housing. The lengthof the locking key is such that when it rests on the plate it holds the handle in a vertical locked position. I

Having briefly described my locking device, it is believed that the various details of the inventioncan be.

vations respectively, partially in cross section, of a portion of the device of FIG. 1.

. FIGS. 3-A, 3-B and 3-0 are front, side and top views respectively of the device of FIG 1.

FIG. 4 is an exploded view of a different part of the device of FIG. 1.

FIG. shows another embodiment of the rope lock of the invention.

FIG. 6 is a section through FIG. 5.

Referring now to FIG. 1, a complete rope brake of the type preferred herein is illustrated in perspective. The brake is shown with rope 12 extending through housing 3, the device being in the locked position. In this locked condition ca-m lever 1, having a handle 4 secured thereto, is vertically disposed with locking key 2 in position against base plate 14.

Housing 3 is shown in greater detail in FIGS. 2-A, 2-B and 2-C. The housing has openings in the top and bottom thereof which permit a rope 12 to be passed through it, end to be moved upwardly and downwardly therein. In addition the front of the housing has a slotted opening 16. Cam lever 1 extends through this slot into the housing. The back of housing 3 is provided with an orifice 18, threaded to receive an adjusting screw, preferably a thumbscrew 13. As can be seen from FIG. 2-B the sides of housing 3 are formed with small holes for rivets or pins which support the working parts of the braking and gripping device.

The operation of the rope lock illustrated can best be seen by referring to FIGS. 3-A, 3-B and 3-C. Referring first to FIG. 3-B rope 12 is seen locked in place by gripping jaws 11. These jaws are pivotally fastened by retaining rivets or pins which are passed through holes in housing 3. Holes are also drilled or otherwise formed in upper gripping jaw sides so that the jaws are suspended at a point near their top ends. The middle and bottom ends of jaws -11 thus are free to move toward or away from each other and from a rope between them. The jaws preferably are cylindrically recessed as shown in FIG. 3-0 to fit about and grip a rope 12.

From FIG. 3-B it can be seen that one gripping jaw is moved forward by thumbscrew 13, whereas the other jaw is urged toward it and against a rope therebetween by cam lever 1. This cam lever is in the form of an L-shaped braking arm extending through opening 1 6 in the front end of housing 3. Cam lever 1 is held by retaining rivet or pin 5, positioning spacers 66 being used to insure strength and rigidity.

Referring again to FIG. 3-B it can be seen that as handle 4 is moved upwardly towards its vertical position, cam lever 1 operates as an eccentric or fulcrumed lever, its cam surface bearing against one of the two gripping jaws 11, bringing about the compression of rope 12 against the other gripping jaw. The rope is thus clamped in a locked position as shown in FIG. 3-B when handle 4 is in a vertical position. Handle grips 4 are secured to cam lever 1 by retaining rivets 8 and washers 9 as shown in FIG. 4.

A prior device provides a retaining ring, encircling rope 12, and adapted to be put over a handle such as handle 4 to hold it in its locked vertical position. However, this involves both hands, and an extra operation. In addition if the flown scenery is heavy it is very difiicult to pull the rope over so that the retaining ring can be slipped over the handle. Consequently the retaining ring is frequently left off of the handle. As a result, handle 4 is easily released. Many times it is bumped or caught by stage hands carrying props and other equipment. This invention overcomes the disadvantage of such rope locks 'by the provision of pivotal locking key 2, which is shown in the form of a stirrup in FIG. 4. The rope lock of this invention also differs from the retaining ring type in the placement of the cam lever pivot. The cam lever in the retaining ring type rope lock is outside the housing, whereas in the rope lock of this invention, retaining pin 5 is within the housing to provide for the attachment of key 2.

Key 2 is connected by means of pin or rivet 7 to cam lever 1 so that it is free swinging under its own weight, due to the force or action of gravity, and so that it will remain suspended, when possible, in a vertical position. Again referring to FIG. 3-B, locking key 2 is so positioned that when cam lever handle 4 is moved forward slightly past the vertical, the locking key, being free swinging (dotted outline), comes to rest in a vertical position between cam -1 and base plate 14. The tension on the system, or gripping pressure, is adjusted previously by setting thumbscrew 13. The length of locking key 2 is such that when it rests on plate 14 it holds handle 4 in its vertical locked position. In the rope lock of this invention the housing is elongated so that the base plate is lower than it is in the retaining ring type rope lock. This permits key 2 to be positioned between the base plate and the cam lever, which would not be possible in the retaining ring type rope lock. The rope lock of this invention thus differs in several respects from prior art rope locks. To the operator or fiyman the rope lock will appear as it does in FIG. 3A.

As can be seen from FIG. 3-B, locking key 2 can be provided with a release hook at its front end. Hence, to change the position of the purchase line the operator merely hooks his finger under the release hook and pulls the key outwardly, while at the same time pulling out wardly and downwardly on handle 4.

Another embodiment of the invention is shown in FIG. 5 and FIG. 6. Referring to the figures it will be seen that locking key 26 is in the form of a rod within handle 20 rather than a stirrup outside the handle. This aspect of the invention also shows a unique means within cam lever handle 20, adapted to displace locking key 26 from its vertical locked position. The release means is shown in FIG. 6. Trigger 22 is held within handle 20 so that its lower end is capable of moving back and forth. Locking key 26, in the form of a rod, contains a protuberant portion near its upper end. When trigger 22 is depressed or squeezed, by pressing against the protuberant part it pushes back locking key 26 to unlock the rope lock handle. Leaf spring 24 restores trigger 22 to its original position.

It will be understood from the foregoing that the rope lock of this invention is eminently suited for use with purchase lines in modern stage counterweighting where speed of operation is a consideration. An additional advantage, as previously indicated, is that a rope lock is provided which can be fabricated of various metals besides the more readily breakable cast iron. Other advantages and variations will occur to one skilled in the art and having been given the teachings of this invention. Thus, whereas base plate 14 is shown drilled for attachment to a locking rail or other device, the rope lock can be welded thereto or otherwise made integral therewith. The locking rail itself can serve as the base plate 14 to support locking key 2. Also a combination floor block and rope lock open type unit can be made for widely spaced rigging sets or doorways where use of a locking rail is impractical. Further, in lieu of a second gripping jaw, the cam surface of cam lever 1 can itself bear against rope 12, being forced against the back jaw, and being provided with teeth if desired. 'In addition locking key 2 need not be stirrup-shaped, but can otherwise be suspended on one side of cam lever 1 or within the handle as shown in FIG. 5. In addition the key can be provided with a weight if desired to cause it more readily to remain in a vertical position. It will be obvious also that use of the rope locking device of this invention is not limited to stage counterweight systems, but

' will lend itself to gripping and controlling various ropes, or

cables, for instance, for the suspension and lowering of life boats, scaffolds, fire escapes, fire fighting equipment and the like. These and such other ramifications as will occur to those skilled in the art are deemed to be within the scope of this invention.

What is claimed is:

1. In a device of the character described as a rope lock comprising a housing having openings in the top and bottom thereof permitting passage of a rope therethrough and a gripping jaw within the housing adjacent its back end, the combination of: a cam, pivotally mounted within the housing adjacent its front end and having a handle extending upwardly therefrom outside the housing, the cam and handle operating as an eccentric lever as the handle is moved toward its vertical position, bringing about the compression of the rope against the gripping jaw, clamping the rope in a locked position when the handle is in a vertical position; with: a locking key pivotally connected to the cam at the base of the handle outside the housing, the locking key being so connected that it is free swinging under its own weight due to the action of gravity, tending to stop in a vertical position, the locking key being so positioned that when the cam lever handle is moved upwardly slightly past the vertical the key comes to rest between the cam and a plate at the base of the housing, the length of the locking key being such that when it rests on said plate it holds the handle in a vertical locked position.

2. The rope lock of claim 1 for use in controlling stage scenery and the like wherein the scenery is manually flown by means of a counterweight system and control rope, wherein the cam lever has its cam surface bearing against a second gripping jaw, and wherein both gripping jaws are held within the housing at only one of their ends, their opposite ends capable of being urged against a rope therebetween, the cam lever urging one jaw, and adjusting screw moving the other jaw closer when adjustment is necessary.

3, The rope lock of claim 2 wherein the locking key is attached within the cam lever and wherein the cam lever handle contains means adapted to displace the key from its vertical locked position.

4. The rope lock of claim 2 wherein the cam lever is an L-shaped braking arm, its cam end extending through an opening in the front end of the housing, its opposite end having a handle grip thereon, wherein the gripping jaws are pivotally attached near their top ends and are cylindrically recessed to fit about and grip a rope, wherein the adjusting screw is a thumbscrew and wherein the locking key is in the form of a stirrup having a release hook at the front end thereof.

5. The rope lock of claim 4 wherein except for the handle grip the device is made of steel.

6 The r-ope lock of claim 5 wherein the base is a steel flange fixed to the base of the housing.

7. The rope lock of claim 5 wherein the base is that portion of the locking rail secured thereto at the base of the housing.

References Cited UNITED STATES PATENTS 1,305,353 6/1919 Gidson 24134 2,322,651 6/1943 Macchesney 2'4134 3,179,994 4/1965 Meyer 23l34 EVON C. BLUNK, Primary Examiner.

H. C. HORNSBY, Assistant Examiner.