AU617699B2

AU617699B2 - Lift sheave

Info

Publication number: AU617699B2
Application number: AU24185/88A
Authority: AU
Inventors: Gregory Eckersley
Original assignee: Johns Perry Industries Pty Ltd
Current assignee: Johns Perry Industries Pty Ltd
Priority date: 1985-11-04
Filing date: 1988-10-24
Publication date: 1991-12-05
Anticipated expiration: 2006-10-30
Also published as: AU2418588A

Description

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AUSTRALIA 617699 PATENTS ACT 1952 Form COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: a 4s 00 4 0 4 4 o 0 0 0 00 4 o o i. 0 0~ o 3 ^Q Priority: Related Aft: Divided from 64611/86 TO BE COMPLETED BY APPLICANT Name of Applicant: JOHNS PERRY INDUSTRIES PTY LTD Address of Applicant: WANGARA ROAD, CHELTENHAM, VICTORIA 3192

AUSTRALIA

Actual Inventor: Gregory Eckerlsey and Maxwell Thomas Jones Address for Service: GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

Complete Specification for the invention entitled: LIFT SHEAVE The following statement is a full desctiption of this invention including the best method of performing it known to me:rl- i 2eg o 0 This invention relates to a lift for raising 0.Lift sheaves ar well known ant generally include a 030 3 0 03 0 03 0 0 3 oo e i 0 Go 0 3 a 3 first portion about which a cable is driven by rotation of the sheave to raise and lower a lift car. The sheave may include a reduced diameter portion for receiving the cable and a larger diameter portion whih includes a brake surface for engagement by brake shoes, arranged outwardly of the sheave, for stopping rotation of thhe sheave to hold a lift car at a desired position in the lift well. The sheave is driven by a motor via a rotatable shaft upon which the sheave is mounted.

3- The rotatable shaft is relatively long since it passes through the motor and the sheave and the shaft is supported by suitable bearings at its ends and usually at an intermediate position between the motor and the sheave. The mutor is actuated to rotate the shaft and thereby rotate the shedve to raise or lower the lift car. In order to stop the lift car at a desired position the motor is stopped and -the brake shoes which are biased against the brake surface on the sheave, engage the sheave to hold the lift at the desired pusition.

When it is desired to move the lift car the motoAi. is activated and the brake shoes are biased away from the brake surface by a solenoid to allow the sheave to rotat-e so the lift car can be moved.

Parent Application No. 64611/86 explaii.s that conventional sheave and motor arrangements suff-er from a S number of drawbacks. The first drawback is concerned with the need to provide a relatively long drive shaft which is driven by the motor. In conventional sheave and motor arrangements the arrangements are therefore largo and the fact that a relatively long shaft is provided means that the ;nhaft must 00. 0 0 generaliy be very accurately aligned. Any misalignment can cause damage to the shaft, the sheave, and/or the motor.

S Furthermore, due to the loads applied to the shaft any 0 imperfection in the shaft may lead to fracture of the shaft.

The invention disclosed in the parent application 0 comprises a sheave arrangement for raising and lowering a lift car, said sheave arrangement being mounted on a static shaft 4 and including a sheave having a first portion for receiving a cable which is adapted to be coupled to the lift car, said sheave h1aving a second portion having a drive means arranged radially adjacent -thereto for ro.,*ating said sheave and a third portion of said sheave having brake means arranged adjacent thereto for holding said sheave stationery with respect to 4 said shaft, said first and second portio'ns of the sheave, and therefore said drive means and brake means, being coplanar in a plane substantially normal to the shaft.

Since the sheave arrangement includes a static shaft and the drive means is arranged radially adjacent to a portion of the sheave the shaft can be made small and the device is therefore very compact. in view of the compact structure of the sheave, according to this invention, the sheave will be economic to manufacture and can be installed in limited space whilst overcoming problems associated with the need to provide a relatively long rotatably driven drive shaft. Furthermore, sincr the drive shaft is a static shaft the loads suppl-'ed to the snaft are not as great or have components in the same directions as in the case of driven drive shafts and the drive shaft is therefore unlikely to fracture and is easy to mount.

Preferably the second and third porticns of the C, 0 0 sheave are inner and outer surfaces of the sheave. which are axially spaced from said first portion of the sheave.

Preferably the drive means is arranged adjacent to the outer surf ace of the sheave and the brake means is arranged adjacent to the inner surface of the sheave and includes brake shoes which can be driven against the inner surface of the sheave to stop the sheave.

Preferably the drive means is a drive motor and the drive motor is either a synchronous motor or an induction motor.

a Preferably the sheave incl~udes support arms which extend radially outward'Ly from said shaft for supporting windings of said drive motor about the circumference of tne outer surface of -the sheave.

Preferably the support means holds actuators such as solenoids, which hold said brake shoes away from the inner surface of the second portion of the sheave against the bias of biasing means, such as a spring, which bias the brake shoes -towards the inner surface of the sheave, said actuators being L r 5 deactivated when the lift car is stopped so that tht brake shoes are biased by the biasing means against the inner surface of the sheave to prevent rotation of the "hleave.

The present invention is also very much concerned with providing a relatively small and compact sheave ari'angement. The aspects of the invention described above do result in a more compact sheave arrangement than has been proposed in the past. However, a further aspect of the invention is concerned with further reducing the size of the sheave arrange:nt.

The invention provides a sheave arrangement for raising and lowering a lift car, said sheave arrangement having a sheave mounted for rotation by a drive means, said o •sheave having a portion for receiving a cable which is a 15 adapted to be coupled to a lift car, drive means for rotating said steave and brake means for stopping and holding said sheave stationary, said drive means including a plurality of stationary magnetic elements and a plurality of magnetic elements arranged for movement relative to the stationary magnetic elements, sail brake means being arranged in proximity to said movable magnetic elements so Sa that said brake a a a Boa amaa rrr means forms part of the magnetic circuit between adjacent magnetic elements in said plurality of movable magnetic elements.

The above arrangement avoids the need to utilize a separate magnetic core for completing the magnetic circuit between the plurality of movable magnetic elements and therefore assists in decreasing the weight and size of the sheave arrangement according to this aspect of the invention.

The magnetic elements may be electro-magnets, permanent magnets or flux switches.

Preferably the brake means includes a brake drum and a movable brake shoe, said brake drum being arranged adjacent said movable magnetic elements and said brake drum completing V^ the magnetic circuit between adjacent magnetic elments.

15 .A furthr ap.at ofkthis invention i con-::rned with pre-exciting the motor whilst the brake is appl-nd that the load in a lift car is balanced by the pre-excitation of the motor when the brake is released. Conventional sheave arrangements and lifts do include a system for achieving this 20 result. However, the conventional systems generally utilize a .O device for measuring the weight or load in the lift car and S0 then pre-exciting the motor to compensate for that load so ooo that when the brake is released the excitation of the motor is sufficient to enable the lift car to move smoothly aware from 0 25 the stationary position. If the motor is not pre-excited there is small delay after release of the brake before the motor commences to move the lift car which means that the lift S" car may be jerked or dropped or raised slightly before the motor is energized to move the lift car. The conventional technique of measuring the car weight or load does not always provide an accurate indication of the amount of pre-excitation which is required. re-FeVr -A furth r acp t ofrthe present invention provides a sheave arrangement for raising and lowering a lift car, said sheave arrangement having a sheave said sheave having a I portion for receiving a cable adapted to be -oupled to a lift car, drive means for driving said sheave and brake means for stopping and holding said (heave stationary, sensor means for sensing the load on said bi means when the brake means is holding said sheave stationaty and control me-ans for pre-exciting said drive means in accordance with the load sensed by the load sensing means.

Since -this aspect of the invention senses the load on the br-ake means a very accu...ate indication of the amount of pre-excitation required to balance the motor and lift car after the brake is released can be obtained. Therefore, the correct amount of pre-excitation can be applied tc, the motor to ensure that the lift car is smoothly mioved from the .00174 stationary positioni whon the brake is released.

A preferred embodiment of the invention will be described in detail with reference to the following drawings in which: CIO Figure 1 is a front view of a sheave embodying the invention; Figure 2 is a cross-sectional view of the sheave of Figure Figure 3 is a view along the line 3-3 of Figure 2; Figure 4 is a more detailed view of part of Figure 2; Figure 5 is a view similar -to Figure "I showing further developments to the emb~odimnent described with 0 reference to Figure 2 and further ill~ustrating varzious components of the embodiment of Figure 1 and Figure 2; Figure 6 is a cross-sectional view of the sheave of~ Figure Figure 7 is a circuit diagram illustrating operation of one aspect of the embodiment of Figure 3; and Figure 8 is a detailed view of part of the embodiment of Figure 3.

With reference to Figures 1 to 4 the sheave arrangement 10 includes a sheave 11 having a first portion 12 which is mounted on a static shaft 14. The first portion 12 may include grooves 16 on its outer circumference for receiving a cable shown schematically at 18 which is adapted to be coupled to a lift car (not shown) The first portion 12 of the sheave has an integral second portion 20 which is of larger diameter than the first portion 12 and is axially spaced from the first portion 12. The first portion 12 may include surfaces 22 and 24 which are machined for a reader disk and for sliprings respectively.

The shaft 14 is mounted by a pair of mounting brackets 30 which are support-I on rails 32 which are adapted to be secured at the top of a ift well (not shown). Le 15 first portion 12 may inclu( c bearings 34 for rotatably supporting the first portion 12 on the shaft 14. Three support arms 40, 42 and 44 are. mounted on shaft 14 and extend radially outwardly thereof. The outer ends of the support arms 40 to 44 extend generally parallel to the shaft 14 and 20 support a plurality of laminations 46 which in turn support windings of a drive motor for driving the sheave portions 12 and 20 about shaft 14.

The internal surface 21 of the second portion forms a surface or brake drum for receiving a brake shoe which is biased against the inner surface 21 of the second 0 portion 20. The brakie srioe 50 is pivotally coupled at one end to a pivot pin 52 on a sunport, member 54 which is secured to F.'1w-ft 14. The other end of the brake shoe 50 is ?ivotally coupled on a pin 55 which is retained on a stud 56 secured to a plate 58. The plate 58 is in turn clamped -to shaft 14 by a clamp assembly 60. The brake 50 includes a drive arma 62 which is pivotally coupled to an adjustment mechanism 64 by a pivot pin 66. The adjustment mechanism 64 includes a plate 68 which has a pin 71 and which is coupled to the brake shoe 50. It should be noted that another brake shcle 50 is provided on the

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0 04 04 404 4 9 44 04 0 4 40 44 0 4 44 4 40 0 00 44 0 4 40 4 00 0 0 4 0 00 0404 4 4 4-440 0 0~ ~044 4 4 0044 0400 04 4 4 44 4 04 diametrically opposite side of the inner surface 21 of the portion 20 (see Figure The drive arm 62 has at its free end a solenoid 70 which when activated draws the drive arm 62 in a direction to move the brake shoe 50 away from the inner surface 21. The drive arm 62 of the diametrically opposite brake shc-e 50 a1pc includes a solenoid represented by reference 72 for drawing that brake shoe away from the inner surface 21. A spring 57 is arranged to bias the brake shoes towards the inner surface 21 of the second portion 20 such that when the solenoid 70 and 72 are deactivated the brake shoes 50 are free to move under the bias of the spring 57 into engagement with the inner surface 21 to prevent rotation of the sheave.

Accordingly, in order to rotate the sheave to raise or lower a lift car the drive motor which is arranged radially outwardly of -the second portion 20 and which is supported by the support arms 40 to 44 i~s activated to rotate the sheave about the shaft 14 and the:reby raise a lift car (not shown) which is coupled to the cable 18. To stop -the lift car at a 20 desired position in a lift well, such as at a floor level, the motor is deactivated to stop thn lift car and the solenoids and 72 are deactivated to enable the spring to bias brake shoes 50 into engagement with the inner surface 21 of the portion 20 to prevent rotation of the sheave. When it is 25 desired to continue movement of the lift car, the solenoids and 72 are activated to draw the brake shoes 50 away from inn%:.r surface 21 against the bias of the spring and the motor is activated to drive the sheave -to raise or lower tho lift car.

This embodiment of this invention therefore has the advantage that the arrange-,ent is extremely compact in view of the drive motor, the second portion 20 of the sheave and tite brake being in a generally radial plane and all being gene.-ally co-planar. In view of this arrangement the 8tatic, shaft is relatively small and the arrangement is therefore very compact. Furthermore, the loads which are applied to the shaft 14 are unlikely to damage or fracture the shaft.

A further advantage of this embodiment of the invention is that mechanical amplification of the braking power can be provided in one direction of rotation of the sheave. In this regard the brake shoes 50 can be arranged relative to the inner surface 21 of the portion 20 such that the sheave can be rotated to raise or lower a lift car by releasing one of the brake shoes and ny activating the drive motor to rotate the sheave against the other brake shoe. As is shown in Figure 3 the configuration of the brake shoe will enable slipping of the sheave in one direction since 00 rotation of the sheave in the direction of arrow A will cause 15 the brake shoe 50 to lock securely against the inner surface o 21 of the second portion 20 whereas rotation of the sheave in the direction of arrow B will allow slipping of the brake shoe S 50 qqainst the inner surface 21. Thus if one of the brake shoes 50 is released slippage in one direction can occur.

20 This may be advantageous when a lift stops at a floor since Swhen the lift is loaded by people walking into the lift car the weight of the people in the car can cause stretching of o0 the cable which causes the lift car to drop slightly relative to floor level. By releasing ap appropriate one of the brakes u ouo 50 and activating the drive motor, slippage can occur in one direction to move the lift car so that it is releveled with S the floor at which the car is stopped.

The embodiment shown in Figures 5 to 8 is similar to that previously described and like reference numerals represent like parts to those shown in the previous embodiment. In this embodiment details of the drive motor M is more fully described. The drive motor generally comprises a plurality of stationary magnetic elements 90 which are spaced apart by coils 92. Arranged radially inwardly of the magnetic elements 90 are a plurality of movable magnetic rrelements 94 which are mounted on the portion 20 of the sheave which forms a drum of the brake for stopping and holding the sheave. Caps 95 hold the element 94 in place and also serve to secure coils 96 between the elements 94. The magnetic elements 94 may be electromagnets, permanent magnets or flux sw~tches. If the magnetic elements 94 are electromagnets it is preferred to include the coils 96 between adjacent elements 94. However if the elements are permanent magnets or flux switches then coils need not be used and spaces may merely be provided between the magnetic elements. The magnetic elements 94 are arranged adjacent to the portion 20 of the sheave which forms the drum brake against which the brake shoes 50 apply a oo o braking force to stop rotation cf thf sheave and hold the So° sheave stationary. The portion 20 of the sheave completes the 15 magnetic path between adjacent elements 94. In order to drive the sheave the elements 90 are excited in a predetermined 4o o sequence by known means and in a known manner "o cause one of the elements 94 to move towards the excited element 90. By continued excitation of the elements in a particular pattern, o, a, 20 the movement of the elements 94 and the second portion 20 to S0 which the elements 94 are coupled, enables the portion 20 to rotate about the shaft 14. By the appropriate control of excitation of the elements 90, the rotation may be in either S direction enabling a lift to be raised or lowered.

S 25 The electro-magnet 70 for actuating the brake shoes 50 via the drive arm 62 includes a flux sensor shown o sschematically at 98 for sensing the flux between the electro-magnet and the drive arm 62. A position sensor (not shown) may also be arranged to sense the position of the drive arm 62 relative to drive an electro-magnet 70 which is used in this embodiment in place of the electro-magnet of Figures 1 and 2. The flux sensor and/or the position sensor is utilized to cause smooth actuation of the brake.

_I Figure 7 shows a circuit diagram for controlling operation of the brake. With reference to fxgure 7, the electro-magnet 70 includes a magnetic coil 70a which is powered by a power amplifier or driver 73. The power amplifier receives a signal from a control and equalization circuit or from a digital or analogue computer 75. Since such computers and control Wircuits are well known full details need not be given herein. The flux sensor 98 is arranged to sense the flux between the electro-magnet 70 and the drive arm 62. (It should be noted that the electro-magnet is shown in electrical form and represented by reference 70a and in to the right in mechanical form. The flux sensor is coupled to the control and equalization circuit 75 via line 77. The position sensor represented by reference 79 in Figure 7 is coupled to 15 sense the position of the drive arm 62 relative to the 0 0 oo electro-magnet 70. The position sensor is coupled to the control and equalization circuit 75 via line 81. A current sensor 83 is arranged to sense the current passing through the magnetic coil 70a. The current sensor 83 is connected to the 0 20 control and equalization circuit 75 via line 85. A voltage sensor 87 detects the voltage applied to the magnetic coil and is coupled to the control and equalization circuit via line 89. A damping resistor or damping strap 91 may be S arranged in parallel to the magnetic coil 25 The flux sensor 98 may be a Hall effect device, a o0g magneto resistor, a pickup coil or a magneto optic device such 0: as a Kerr effect device. The flux sensor detects the magnetic flux between the electro-magnet 70 and the drive arm 62 and applies a signal indicative of the flux strength to the circuit 75. When an on/off command is applied to the control circuit 75 from the main lift controller to cause the brake to be released or applied, a signal is outputted from the control and equalization circuit 75 to the power amplifier 73 and then to the magnetic coil 70a. Assuming that the brake is to be eleased so that the sheave can rotate the arm 62 is drawn by 3:, P 7^'A k4t i '~Rur "3 the electro-magnet 70 in the direction of arrow A to cause the arm 62 to release the brake shoe 50. If the current supplied from the power amplifier 73 is not altered then as the arm 62 moves towards the electro-magnet 70 flux will increase and the arm 62 will tend to slam shut causing a rapid release of the brake shoe 50 from the brake drum 20. However, in this embodiment of the invention the flux between the electro-magnet 70 and the arm 62 is sensed and as the flux increases the flux sensor 98 applies a corresponding signal to the control and equalization circuit 75 which in turn causes the voltage outputted from the power amplifier 73 to reduce to thereby decrease the amount of magnetic flux and this causes o the arm 62 to move smoothly towards the electro-magnet and not to slam closed against the electro-magnet. Thus the brake is 15 smoothly released. The current sensor 83 sensors that the current passing through the magnetic coil 70a is being reduced as does the voltage sensor 87. Once the brake has been released an acknowledgment signal is supplied from the control and equalization circuit o o 20 Similarly, when the brake is released the flux is sensed and as the arm 62 moves away from the electro-magnet the flux can be increased so that the arm 62 moves the brake S shoe 50 smoothly away from the drum o Instead of using the flux sensor 98 to provide an a 25 indication of the flux between the arm 62 and electro-magnet 70, the position sensor 79 may be used to provide an o a indication of flux by sensing the position of the arm 62 relative to the electro-magnet 70 and then determining from that position the flux between the electro-magnet 70 ard the arm 62. Thus, the position sensor may be used instead of the flux sensor in order to sense the flux between the arm 62 and the electro-magnet 70. Alternatively, the flux sensor could be used to determine the position of the arm 62 by deriving the position from the relationship between coil magneto-motive force and the flux.

rw~-~rrm4rs~i~~r~uu ~rr The circuit described with reference to Figure 4 enables smooth operation of the brake and therefore ensures smooth movement of a lift car utilizing the sheave of this embodiment of the invention.

Figure 8 shows a detailed portion of the support arm which surround the shaft 14. In the embodiment of Figures to 8 the support arm is configured differently to that shown in Figures 1 and 2. The support arm 40 has an inner hub portion 51 which receives the shaft 14. The hub portion 51 has an integral arm 53 with a flange 56 for supporting the magnetic elements 90 and coils 92. The hub portion 51 of the support arm 40 includes a pair of lugs 41 which define a space 43a therebetween. Integral with the lugs 41 is a T-shaped portion 43 which has two ends 45 spaced a small distance from S 15 internal surfaces 47 of the lugs 41. The ends of the T-shaped portion have the brake shoes 50 pivoted theioto on pivot pins Arranged on a s" m 49 of the T-shaped portion 43 are strain gauges 61 which measure the load on the brake shoes When the brakes are applied the load acting on the brakes 20 will be transmitted to the T-shaped portion 43 and will tend to cause the T-shaped portion 43 to move as shown by dotted lines and reference by numeral 49'. It should be noted that the movement is exaggerated is Figure 8 for the purposes of illustration, The strain gauges 61 will detect the amount of movement and will produce a signal indicative of the amount of S movement wh. ch, in turn, is indicative of the amount of load acting on the brakes The space 'tween the end portions 45 and surfaces 47 is to allow for an amount of movement equal to a fully 0S loaded lift car. If the lift car is overloaded and there is more load on the brake than is intended the end portions 45 of the T-shaped portion 43 will abut against one of the surfaces 47 to prevent further movement of the T-shaped portion 43 and prevent permanent deformation or breakage of the T-shaped portion 43. The output of th strain gauges 61 is applied to /^J01 \s the lift control system so that an appropriate amount of pre-excitation may be applied to the motor M to cause the motor M to be in balance with the load applied to the brakes and therefore the load in the lift car. When the brakes are released the lift car may therefore be moved smoothly and will not tend to drop slightly, raise slightly or jerk.

The preferred embodiments of the present invention therefore provide a lift sheave which is smaller and lighter compared to previous lift sheaves and in particular to a lift sheave which does not require a heavy base plate to reinforce the sheave which makes up a considerable part of the weight of some conventional sheave arrangements.

Since modification within the spirit and scope of the invention may i .adily be effect-d by perscns skilled S 15 within the art, it i be understood that this invention is not limited to the particular embodiment described by way of example hereinabove.

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Claims

1. A sheave arrangement for raising and lowering a lift car, said sheave arrangement having a sheave mounted for rotation by a drive means, said sheave having a portion for receiving a cable which is adapted to be coupled to a lift car, drive means for rotating said sheave and brake means for stopping and holding said sheave stationary, said drive means including a plurality of stationary magnetic elements and a plurality of magnetic elements arranged for movement relative to the stationary magnetic elements, said brake means being arranged in proximity to said movable magnetic elements so that said brake means forms part of the magnetic circuit between adjacent magnetic elements in 1,1 said plurality of movable magnetic elements. o 15

2. A sheave according to Claim 1, wherein the brake means includes a brake drum and a movable brake shoe, said 0i brake drum being arranged adjacent said movable magnetic elements and said brake drum completing the magnetic circuit between adjacent magnetic elements. DATED THIS 10TH DAY OF SEPTEMBER, 1991 SJOHNS PERRY INDUSTRIES PTY. LTD By its Patent Attorneys: GRIFFITH HACK CO Fellows Institute of Patent Attorneys of Australia.