Abstract:
An arrestor for any hydraulic ram or other cylinder but primarily for an emergency brake for lifting elevators. The present invention is a jack arrestor utilizing two lever acting brake arms lined with an accretable metal as the friction material. When actuated, the brake arms contact the ram circumferentially to slow and stop the falling ram. The lining material is machined inside the brake arms to a diameter slightly less than the diameter of the ram and when actuated, the accretable material on the brake arms contacts the ram with sufficient frictional force to stop the downward motion of the ram. The safety brake may be actuated by loss of hydraulic pressure, by an electronic signal from a hydraulic pressure detector, by down overspeed or by an uncontrolled down motion detector. In the case of the hydraulic pressure detector, reapplication of normal pressure in the hydraulic cylinder will automatically reset the brake.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates generally to safety brakes for hydraulic jacks or rams. In particular the present invention relates to a hydraulic ram lifting elevator emergency arrestor using a lever and lock mechanism to provide braking action without permanently damaging or destroying the hydraulic ram. 
     2. Description of the Prior Art 
     The present invention relates to a hydraulic ram arrestor using a lever lock type of mechanism which is activated by a pressure failure condition, down overspeed, or uncontrolled down motion. When activated, two lever acting brake arms are dropped into contact with the elevator ram, the resulting friction bringing the elevator to a sliding stop. 
     There have been numerous brake systems developed for stopping hydraulic ram elevators during emergency situations. All of the prior art patents found were directed toward collets or brake shoes, that, during a hydraulic pressure failure, would drop down and wedge in between a fixed housing and the ram of the elevator. The friction generated by the downward motion of the ram in contact with the collet or brake shoe causes the collet or brake shoe to be driven downwardly, thereby wedging the ram to a halt. Empirical evidence indicates that the force necessary to stop an elevator using such a brake exceeds the elastic limit of the material used in commercial rams causing the ram to be deformed into an hourglass shape at the point where such brakes grip the ram. This type of damage to the ram cannot be repaired and instead, expensive and time consuming replacement is required to restore the elevator to working condition. The prior art patents also disclosed elevator brakes that have many moving parts, and are correspondingly complex. Additionally, the prior art devices appear relatively large and bulky. Size is an important consideration because there is often limited space into which to fit a braking device. Therefore, it is desirable for the brake to have a low profile, thereby facilitating installation in all present hydraulic elevators. 
     As a specific example of a prior art design having the above mentioned short comings, Beath et al., U.S. Pat. No. 4,449,615 is a floor mounted lever-actuated wedge device. The many components in this design complicate it by comparison to the present invention. Beath uses collets, that, during a hydraulic pressure failure, drop down and wedge in between a fixed housing and the ram of the elevator. The friction generated by the downward motion of the ram in contact with the collets causes the collets to be driven downward, thereby wedging the ram to a halt. The force necessary to stop an elevator using the brake disclosed in Beath exceeds the elastic limit of the material used in commercial rams causing the ram to be deformed into an hourglass shape at the point where the collets grip the ram. Additionally, the above mentioned patent does not precisely show relation to the top of the cylinder and the bottom of the elevator. However, it appears too tall to fit most existing elevator systems. 
     In light of the problems listed above and exemplified by U.S. Pat. No. 4,449,615, a new elevator brake is needed that can safely stop a fully loaded elevator without permanently damaging the ram. 
     The present invention, using an accretable metal or other adherent material to apply a braking force to the ram is a clear improvement over the prior art. Prototype testing has shown that copper bar formed to shape has yielded sufficiently high braking force, with and without the presence of oil on the surface of the ram. Several materials have been tested, and, to date, copper has been the best material for the purpose. The present invention is also comparatively simple and low in profile facilitating installation on current elevator designs. 
     SUMMARY OF THE INVENTION 
     The general object of the present invention is to provide a mechanism for arresting an elevator which can safely stop a fully loaded elevator without permanently damaging any part of the elevator. 
     It is another object of the present invention to provide an elevator arrestor that allows the elevator to be usable within a short period of time with little reset and repair necessary. Optimally, the reset and repair should be a relatively simple and inexpensive procedure. 
     It is a further object of the present invention to provide an arrestor that will fit within a small vertical space such that it can fit within the normal design parameters for hydraulic ram elevators, and may also be retrofit into existing hydraulic ram elevators. 
     It is yet another object of the present invention to provide a system that can be easily installed and requires very little down time in which the elevator is non-functional. 
     It is an additional object of the present invention to provide for an arresting system that is inexpensive to manufacture. 
     The present invention is a hydraulic safety arrestor for slowing and stopping a ram, jack or other cylinder type object. It utilizes two lever acting brake arms lined with an accretable metal as the friction material. When actuated, the brake arms contact the ram circumferentially to slow and stop the falling ram. The lining material is machined inside the brake arms to a diameter slightly less than the diameter of the ram. When actuated, the lining material contacts the ram with sufficient frictional force to stop the downward motion of the ram without deformation of the ram. The rest of the mechanism is comprised of buttress members, pivot pins, and a base plate, mounted above a spacer ring. The spacer ring is the same diameter as the cylinder and is variable in length to raise the base plate and brake assembly above any bolts or other existing projections. Eyelets are welded to the existing cylinder to provide for secure mounting and correct alignment and realignment when the brake is removed and reinstalled. 
     The brake arms may be actuated mechanically by loss of hydraulic pressure, by an electronic signal from a hydraulic pressure detector, by down overspeed or by an uncontrolled down motion detector. 
     The force applied by the braking action is transferred from the brake arms through the base plate and spacer ring onto the circumferential area of the top of the main cylinder and any associated support structures. By monitoring the pressure and overspeed, the fall of the elevator can be limited to speeds with a maximum of less than twice the normal down speed, thus limiting the kinetic energy produced, by not allowing a free falling elevator. Therefore, the pit structure would absorb the energy with damage of deformation, without any modifications to the pit structure. 
    
    
     These and other objects and advantages of the invention will no doubt occur to those skilled in the art upon reading and understanding the following detailed description along with the accompanying drawings. 
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation view showing the brake and control components according to the invention. 
     FIG. 2 is the front elevation view showing the brake and control components according to the invention. 
     FIG. 3 is a sectional view showing the frictional contact, and locations of the packing in relation to the invention, as viewed along the line A—A in FIG.  4 . 
     FIG. 4 is a plan view of the invention, as viewed along the line  1 — 1 . 
     The term “accretable” is used in its conventional sense, meaning that the friction material is able to accrete to or to adhere to the surface of the ram. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The drawings show a safety brake system according to the present invention, indicated generally by the reference number  1 . Although the brake system  1  is applicable to many hydraulic ram or piston devices, it is described here in its preferred use on a hydraulic ram lifting elevator. References to “up”, “down”, “vertical”, “horizontal”, etc. should be understood to refer generally to the relative positions of the components of the illustrated device, which could be otherwise oriented or positioned for non-elevator applications. Further, although the term “hydraulic” is used, this invention could be used on any device with a similar configuration, i.e. a main cylinder which surrounds a second cylinder. References to “hydraulic” should be understood to refer generally to any pressure ram device including but not limited to hydraulic and pneumatic ram devices. 
     In FIG. 1, a reciprocal piston or ram  3  is shown with brake system  1  installed on the existing main cylinder  5 . Spacer ring  7  rests upon the upper end of main cylinder  5  at  9  and is removably fixed to upper end of main cylinder  5  by any one of a number of known fastening means. In a preferred embodiment, the known fastening means comprises eyelets  11  fixed to the outside surface of main cylinder  5  and near the upper end  9  of main cylinder  5 . Each eyelet comprises a pair of flange  15  spaced a short distance apart, and flanges  17  on spacer ring  7  fit in between flange  15  of eyelets  11 . Flanges  17  and flange  15  have bolt holes  19  which are aligned to accept eyelet bolts  20  to fix spacer ring  7  to main cylinder  5 . In an alternate embodiment, eyelets  11  may comprise only a single flange. The advantage of using eyelets  11  is that any one of eyelets  11  can act as a pivot to rotate brake system  1  away from main cylinder  5  to allow access for servicing when eyelet bolts  20  are removed from the other eyelets  11 . Removal of all eyelet bolts would allow total removal of brake system  1  for major work. Eyelets  11  also allow for exact reattachment of the device assuring proper alignment. 
     Base plate  21  is fixed to the upper surface of spacer ring  7  at  23 . Buttress members  25  are fixed to base plate  21  on either side of brake arms  27 . In the preferred embodiment, brake arms  27  are hingably fixed to buttress members  25  by pivot bolts  29  allowing brake arms  27  to rotate into or out of contact with ram  3 . 
     In ready or standby position, brake arms  27  are raised 15 degrees from horizontal, allowing travel clearance of ram  3 , best seen in FIG.  2 . Brake arms  27  are shaped having semicircular cut-outs  26 , best seen in FIG. 4, of diameter slightly larger than ram  3 , and having a friction material mounting surface  28  on the inside of cutouts  26 , best seen in FIG.  3 . An accretable friction material  31  is fixed to the friction material mounting surfaces  28  of half circular cut-outs  26  of brake arms  27 . In a preferred embodiment the accretable material  31  is annealed copper, but other materials may be used. Annealed copper is preferred because, of the materials tested, it has the greatest tendency to adhere to the ram  3 . This maximizes the amount of friction between the ram  3  and the brake lining  31 , which creates the greatest braking force with the least amount of damage/deformation of the ram  3  and the braking system  1 . The inside diameter of the accretable friction material  31  is slightly smaller than the outside diameter of the ram  3 . This provides proper engagement with ram  3  to bring the elevator to a halt. 
     Although the preferred embodiment uses two brake arms  27 , a multiplicity of brake arms could be used. Each of the segments would form a section of the ring around the ram  3 . These sections could be equal in size, or they could be disparate, if desired. Different sized sections could be advantageous in some situations, including where the configuration of the work space makes installation or maintenance easier if a certain portion of the brake system  1  is more articulated. 
     In an alternate brake arm embodiment, not shown, cutting bits or teeth may be fixed to the friction material mounting surface  28  of brake arms  27  in place of or in addition to accretable friction material  31 . In this alternate embodiment, braking is accomplished by the teeth biting into ram  3 . Unlike the hourglassing damage caused by the prior art, the type of damage caused by this alternate embodiment can be repaired by filling and filing the gouges. 
     Other systems for hingly fixing brake arms  27  to buttress members  25  are possible. 
     In an alternate hinge embodiment, hinge bolts may be used. In the hinged bolt embodiment, not shown, the rear side of brake arms  27  opposite the semicircular cut-outs  26  are oriented against buttress members  25  rather than lying between them as in the preferred embodiment. Brake arms  27  are spaced from buttress members  25  a distance sufficient for brake arms  27  to be rotated upwardly 15 degrees from horizontal. A plurality of hinge bolts pass through holes in buttress member  25  into the rear edge of brake arms  27  and are threadably fixed thereto. Bending of the hinge bolts allows pivotal motion of brake arms  27 . 
     In another alternate hinge embodiment, also not shown, a slide hinge may be used. In this alternate embodiment, the side of brake arms  27  opposite the side nearest ram  3  are, again, oriented against buttress members  25  rather than lying between them. Buttress member  25  has a concave channel to partially receive the rear edge of brake arms  27 , and the rear edge of brake arm  27  is rounded to fit the concave surface of buttress members  25 . During pivotal movement of brake arms  27  the rounded rear edges of brake arms  27  slide within the concave surface of buttress member  25 . 
     FIG. 3 shows the brake system  1  in actuated position. Accretable friction material  31  is in contact circumferentially with ram  3 . Further travel downward by brake arms  27  is prevented by contact with base plate  21 . Spacer ring  7  transfers kinetic energy from the brake arms  27  and base plate  21  onto the main cylinder  5  or any associated support structure which may exist. Eyelets  11  and the structural strength of spacer ring  7  prevent brake system  1  from slipping and assure equal transfer of force directly downward, into existing main cylinder  5  or onto any associated cylinder support structures. Kinetic energies can be limited by limiting the down speed allowed before brake system  1  is actuated, thereby preventing damage to the brake system  1 , ram  3  or to the main cylinder  5 . 
     In the preferred embodiment, brake system  1  is actuated by loss of hydraulic pressure detected by direct feedback from the main cylinder  5 , by an electronic signal indicating loss of pressure in the cylinder  5 , by electronic signal from a down overspeed, or by an uncontrolled down motion detector. 
     Brake system  1  is actuated by downward motion of actuation rod  35  attached to the actuation assembly, generally identified by  33 . The top of the actuation rod  35  has a disc shaped metal wafer  37  that is received inside shaped hollows or routs  39  in the brake arms  27 . This assures registration between both brake arms. 
     Hydraulic actuation of brake arms  27  is accomplished by the hydraulic actuation assembly, generally referenced by the number  38 . The hydraulic actuation assembly  38  is located in and around feedback control cylinder  43  which is fixed between upper hydraulic cylinder bracket arm  46  and lower hydraulic cylinder bracket arm  48  of hydraulic cylinder bracket  55 , both bracket arms  46 ,  48  being fixed to hydraulic cylinder bracket  55 . The hydraulic actuation assembly  38  comprises feedback cylinder  43  having portal  41  to receive the lower end  46  of actuation rod  35 , plunger  47  fixed to the lower end  46  of actuation rod  47 , and helical compression spring  45  which is engaged over and around the lower end  47  of actuation rod  35 , one end of compression spring  45  engaging the inside surface of the top of feedback cylinder  43  and the other end engaging plunger  47 . 
     Helical compression return spring  45  urges plunger  47 , and actuation rod  35  fixed thereto, downward. Under normal conditions, hydraulic pressure in feedback cylinder  43 , in fluid communication with main cylinder  5 , overcomes the compressed spring energy of return spring  45 , urging plunger  47  upward, which in turn urges control rod  35  upward, which then urges brake arms  27  into ready or standby position. 
     Loss of hydraulic pressure in the main cylinder  5 , is communicated to feedback cylinder  43  through hose  49  (FIGS.  1  and  2 ). Return spring  45  overcomes the reduced pressure in feedback cylinder  43  urging plunger  47  and attached actuation rod  35  downward pulling brake arms  27  into contact with ram  3 . Friction resulting from contact of accretable material  31  on the friction material mounting surface  28  of brake arms  27  urges brake arms  27  further downward into contact with ram  3  until brake arms  27  rest on horizontal base plate  21 . The accretable friction material  31  on brake arms  27  grips ram  3  with sufficient frictional force to stop the downward motion of ram  3 . 
     Electronic actuation of brake arms  27  is accomplished by the electronic control assembly generally referenced by the number  40  comprising control bracket  57  fixed to spacer ring  7 , upper solenoid bracket arm  61 , and lower solenoid bracket arm  63 , both being fixed to control bracket  57 . Electronic actuation assembly  40  further comprises, electronic activator rod  59 , and helical compression support spring  51  placed over and around electronic actuation control rod  59 , the upper end of support spring  51  engaging lower surface of hydraulic control assembly  38 , and the lower end of support spring  51  engaging the upper surface  51  of solenoid bracket  61 . 
     In the preferred embodiment, electronic activator rod  59  is fixed at its upper end, generally, to the hydraulic actuation assembly  38 , which is slidably engaged with slide bracket  44 , slide bracket  44  being fixed to control bracket  57 . 
     Solenoid helical compression support spring  51 , is selected to support the weight of brake arms  27  and hydraulic actuation assembly  38 . Tubular solenoid  65  is fixed between upper and lower solenoid bracket arms  61  and  63 . The lower end of electronic actuation rod  59  partially penetrates tubular solenoid  65 . The upper end of electronic actuation rod  59  is coupled to the underside of lower hydraulic cylinder bracket arm  48  of hydraulic cylinder bracket  55 . An electronic signal from a down overspeed detector or uncontrolled downward motion detector, not shown, causes an electric current in solenoid  65  generating a magnetic field of strength sufficient to urge electronic actuation rod  59  downward into tubular solenoid  65 , thereby pulling the entire hydraulic actuation assembly  38 , slidably engaged to slide bracket  44 , downward thereby actuating brake arms  31 . 
     In an alternate embodiment, not shown, the electrical actuation assembly  40  is the same as described above, except no hydraulic actuation assembly  38  is used. Instead, electronic actuation rod  59  is engaged directly with brake arms  27 . In this alternate embodiment, an electronic signal from a hydraulic pressure detector could also be used to actuate electronic actuation assembly  40 , in addition to a down overspeed or uncontrolled downward motion detector. 
     A variety of known down overspeed or uncontrolled downward motion detectors are available for use with this invention. For example, devices such as those disclosed in Coy, U.S. Pat. No. 4,638,888 which discloses an electronic system for detecting the hydraulic pressure in an elevator ram piston cylinder, and Ericson, U.S. Pat. No. 5,052,523 and Sobat, U.S. Pat. No. 3,942,607, which both disclose mechanical means for detecting the downward speed of an elevator. The specifications of these patents are hereby incorporated by reference in their entirety. 
     Given the generally small distance from the bottom of a standard hydraulic lift elevator to the top of the existing piston cylinder structure, a low profile device is desirable. The present device, in ready position is between four and five inches high. This is accomplished by keeping the fulcrum angle at 15 degrees as shown in the drawings, best seen in FIGS. 1 and 2. Therefore, it is easily mounted onto all existing elevator cylinders. 
     Packing  16  is shown in FIG. 3 for illustrative purposes only, and varies from elevator to elevator depending on the manufacturer. The length of spacer ring  7  is dependent on the packing mechanism used by the various makes. 
     In general, the packing of all rams is located in the cylinder head at the top of the cylinder. The packing is the seal which retains the oil pressure and allows the smooth ram wall to slide relatively freely through it. Generally, there is some bypass of oil through this seal. When this bypassed oil is excessive it is customary to change the packing. As common as this procedure is, it is desirable to allow easy and open access to the cylinder head. As explained previously, the present invention utilizes a three point eyelet mounting. Any one of eyelets  11  can act as a pivot to rotate brake system  1  away from main cylinder  5  to allow access for servicing. By assuring enough range of motion by having a feedback hose  49  and electrical wiring of sufficient length, the device is easily rotated for access to packing  16  without the need to disconnect electrical wiring or hydraulic connections. 
     National, state and local codes provide regulations for periodic testing of safety devices, so it is desirable to retest without damaging either the ram or the brake. Prototype testing to date has shown less than twenty thousandths of fin inch deformation of the annealed copper at the open edges of the annealed copper bar, where the brakes meet centrally when closed, and no deformation elsewhere. Thus periodic testing is available, and the common practice of blocking the elevator to serve as a stable working platform is easily done by manually setting the brake. 
     The preferred embodiment described herein is illustrative only and although the examples given include many specificities, they are intended as illustrative of only one possible embodiment of the invention. Other embodiments and modifications will, no doubt, occur to those skilled in the art. Thus, the examples given should only be interpreted as illustrations of some of the preferred embodiments of the invention, and the full scope of the invention should be determined by the appended claims and their legal equivalents.