US 3533188 A
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Description (OCR text may contain errors)
Oct. 13, 1970 p, JONES ETAL 3,533,188
DOOR OPERATING MECHANISMS Filed Oct. 22, 1968 3 Sheets-Sheet 1 D.C. SUPPLY 56 CONTROL. 55
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DOOR OPERATING MECHANISMS Filed Oct. 22, 1968 3 Sheets-Sheet 2 IlvvEAn-oRi: leaf [6:41; Jan: on 75mm Glut/r J E 5 Q I l/rramvcvz Oct. 13, 1970 p, JONES ETAL DOOR OPERATING MECHANISMS 3 Sheets-Sheet 3 Filed Oct. 22, 1968 I veuraos: -H Lislm Jon: Jon 70 001? Gkmrnw s" United States Patent 3,533,188 DOOR OPERATING MECHANISMS Peter Leslie Jones and John Tudor Griflith, Capenhurst, England, assignors to The Electricity Council, London, England, a British body corporate Filed Oct. 22, 1968, Ser. No. 769,496 Claims priority, application G521; Britain, Oct. 23, 1967,
Int. 53]. E05f /00; H021: 41/02 US. Cl. 4936 4 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention This invention relates to door operating mechanisms for opening and closing doors where motion is required in the plane of the door. It is applicable to sliding doors or to folding doors.
Description of the prior art Pneumatic and hydraulic drives for linearly movable doors are commonly preferred to electro-mechanical systems with rotating drives because of the complexity of the linkages and the severe conditions imposed, e.g. the requirement to be able to reverse the motion at any point in the stroke.
SUMMARY OF THE INVENTION This invention makes use of a linear electric motort Linear motors operated by alternating current are well known. These are generally induction motors driven [from a polyphase alternating supply and they have force-speed characteristics generally analogous to those of rotary in duction motors. However this type of characteristic is not suitable for door operating mechanisms where it is required to start the door moving from rest and to open it quickly.
We have found however that it is possible to make a door operating mechanism using a form of linear electric motor which is analogous to a direct current operated motor and, according to the present invention, a door perating mechanism for giving linear motion to a door comprises a linear electric motor having a field coil assembly and armature linearly movable relative to one another the armature being an elongated member on which is wound a coil at least one part of which is energised with direct current through brushes on the field coil assembly and means connecting the movable part of the motor to said door. By using a direct current linear motor, a high thrust is obtained at the start to overcome the inertia and static friction. During movement, there is speed balance against rolling friction and it is readily possible to slow the door down at the end of the stroke by changing the field and/ or armature current In a preferred form of construction, the door operating mechanism comprises a linear motor having an armature and field coil assembly, the armature consisting of a bar Patented Oct. 13, 1970 ice of ferro-magnetic material with an electrically conductive coil wound around the bar but insulated therefrom and the field coil assembly being linearly movable relatively to said bar, said field coil assembly including brushes con-= tacting the coil on the bar to feed direct current through a portion of the coil, a ferromagnetic assembly which, with part of the bar, forms a magnetic circuit and at least one field coil fed with direct current for producing a flux in said magnetic circuit, the brushes being arranged to energise at least one part of the coil where the magnetic flux passes across the coil between the bar and the external magnetic circuit and either said field coil assembly or said armature whichever is the movable part, being connected to said door.
The form of direct current linear motor actuating sys= tem described above has particular advantage when used for actuating a door in that the armature conductors are enegrised only over a short part of their length between the bushes; hence any given part of the armature is energised only temporarily as the field coil assembly moves relatively to the armature. It thus becomes possible to use large armature currents with a modest size of armature conductor. Moreove, the ease of speed contol of a direct current motor gives smooth operation of the door, and, particularly, a reduced speed when approaching the limit positions is readily achieved. In addition the power input requirements when providing thrust at low speeds are small.
For some forms of sliding door, for example doors on tube trains, there is room on one side of the door to accommodate a long operating mechanism and conven iently in this case, the armature is preferably made mov able and is coupled to the door, the field coil assembly being fixed. This obviates any need of flexible connec-= tions or sliding contacts for supplying power to the field coils or to the brushes feeding the armature coil. In other cases however, such as for example lift or elevator doors, there may be. insufficient room to make the armature movable and in this case the field coil assembly may be movable. Often in such cases the amount of travel of the door is limited and conveniently power is supplied to the field coil assembly via a pivoted arm which may house a flexible cable.
Preferably two pairs of blushes are provided for ener gising two sections of the armature coil in opposite senses. One brush may'be common to the two pairs. In such a construction, the field coil assembly may have two pole pieces located ,respectively between the brushes of the two pairs and two further pole pieces, one beyond each end brush. The thrust can be increased however by providing more poles. In one convenient form of construc tion employing four poles, there is one magnetic circuit between the first inner pole and a second inner pole, the circuit being completed through the armature in one direction and back through the external ferro-magnetic part of the field coil system and there are second and third magnetic circuits through the armature in the opposite diection from each inner pole to an adjacent outer pole and back through the ferro-magnetic part of the field coil system. Three brushes may be provided located between successive adjacent pole pieces. Assuming all the poles are similar and the magnetic circuits have similar windings and all have an armature of constant cross section, the maximum flux at each of the inner poles is now twice the flux through the armature. The thrust, which is the product of current density and flux, is thus doubled for the same armature current compared with a two-pole system.
Most conveniently the magnetic circuit is energised. by a field coil or coils coaxial with the armature,
3 BRIEF DESCRIPTION OF DRAWINGS FIG. 1 -is a diagram illustrating the general arrange ment of a. sliding door and its operating mechanism suit= able for use on a railway coach;
FIG. 2 is a diagram in plan and partly in section illus-= trating a construction of linear electric motor for use in the mechanism of FIG. 1;
FIG. 3 is a diagram for explaining the operation of the motor of FIG. 2;
FIG. 4 is an end elevation of the fixed part of the motor of FIG. 1;
FIG. 5 is a view similar to FIG. 3 of another construc tion of motor; and
FIG. 6 is a diagram illustrating the operating mechanism of a door for an elevator.
Referring to FIG. 1, there is shown diagrammatically a door 8 slidable in guide rails 9 in the directions indicated by the arrows 11. The door is coupled by a. coupling 10 to an armature 12 which. co-operates with a fixed field coil assembly .7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The armature and field coil assembly are shown in fur ther detail in FIGS. 2 to 4. The movable armature 12 consists of a bar of mild steel around which is uniformly wound an armature coil 13. The coil is formed of insulated copper wire with the insulation removed along a strip on one face to form a commutator surface. This armature coil is energised over two portions of its length by means of two pairs of brushes, one brush 16 being common to the two pairs and located between the other two brushes 15, 17. The current fed through these brushes is such that the fiux produced in the two portions of the armature is in opposite directions. These brushes are carried on a fixed assembly including a field coil and associated magnetic circuit. The magnetic circuit is consti= tuted by ferro-magnetic members 20 having four pole pieces 21, 22, 23 and 24 substantially encircling the armature 12. In the particular arrangement illustrated three field coils 25 are provided which are coaxial with the armature 12 but are mounted in the ferromagnetic member 20 so as to be fixed relative thereto, these coils being located between the pole pieces.
In the construction illustrated in FIGS. 2 to 4, the field coil assembly is enclosed within a housing which has top, bottom and side walls of non-ferrous material. At each end, guide blocks 31 of polytetrafluoroethylene steady the assembly against lateral movement. In the vertical direction, the armature 12 is supported on guide wheels 32 engaging the underside of the armature.
FIG. 3 is a diagram illustrating the flux paths. It will be seen that, if the field coils 25 are energised, then a first magnetic flux circuit indicated by the dashed line 26 is produced through the ferromagnetic member 20 between the two inner poles 22, 23, and is completed through the armature 12. Second and third magnetic fiux paths 27, 28 are produced between the inner pole 22 and outer pole 21 and between the inner pole 23 and outer pole 24 respectively. In each magnetic circuit, the flux cuts the armature winding 13 adjacent the pole pieces. These portions of the armature winding are energised and thus a mechanical force is established between the current carrying conductors on the armature and the fixed field coil assembly. This causes the armature to move. As the armature moves, the appropriate section of the armature winding is always energised by the brushes and hence the armature moves continuously. This particularly linear motor system is analogous to a rotating direct current motor and thus it provides substantial thrust at low speeds of operation. Because the armature winding only carries current through a limited portion of its length, this portion changing as the armature moves, it is possible to have a large armature current with a modest size of armature conductor. Reversal of movement is effected by switching either the field current or the armature current. With the four pole system described above, if A is the armature crosssection and B is the saturation flux density of the armature core material, it will be seen that the maximum flux at the inner poles 22, 23 is 2B A which is twice that of a corresponding two pole structure and hence the thrust of the motor is doubled compared with a two pole structure.
The armature may be of round section as shown in FIG. 4 or of other section. If it is round, an indexing de vice, not shown, may be provided for rotating the armature to ensure even brush wear around the periphery of the armature coil.
It is often convenient however to use an armature which is not round. FIG. 5 illustrates an armature of generally rectangular section, the shorter sides being rounded to facilitate keeping the armature winding close to the armature surface all round the periphery. In FIG. 5, the armature is shown at sliding on a polytetrafiuoroethylene block 41 in the field coil assembly. Two pole pieces 42 are shown together with a field winding 43 and a housing 44 of non-ferrous metal. Multiple poles may be provided as described with reference to FIGS. 2 and 3. It will be seen that the construction of FIG. 5 permits of a particularly compact section for the field coil assembly.
If the motor is to be used for a door where there is not room to move the armature, then the armature 12 may be fixed and the door may be carried with the field coil assembly. Such an arrangement may be used for a lift or elevator door, as is illustrated diagrammatically in FIG. 6. In this figure there there are shown a fixed armature and a field coil assembly 51 slidable along the armature. This field coil assembly is connected to a member 52 forming part of the door by means of a resilient COl1-' pling 53. In this case the field coil assembly may be energised by sliding contacts engaging a pair of conductor rails adjacent the track or by trailing leads supported by a Bowden cable or most conveniently by flexible leads taken through a pivoted arm.
In FIG. 6, the feed is illustrated as a flexible lead 54 between the field coil assembly 51 and a control unit 55 which controls the application of direct current from a supply source 56 to the field coils and armature. This control unit may be operated in the known way by manually operated push button controls together with limit switches. Limit switches at each end of the stroke are provided to interrupt the field current and armature current. For slowing down the door just before each end of the stroke further limit switches are provided which increase the field current and reduce the armature current for the last part of the stroke. Reversal of the motion may be effected by reversing the polarity of the field current or the armature current; preferably the field current is reversed as it is much smaller than the armature current. The control unit would usually be arranged to provid immediate reversal of the motion should the door meet an obstruction, this being detected by a rubber faced strip on the leading edge of the door, which strip operates a switch if it comes into contact with an obstruction. It will be particularly noted that a direct current linear motor can rapidly and easily be reversed to meet this requirement.
1. A door operating mechanism for giving linear mo" tion to a door comprising a linear electric motor having a field coil assembly and armature linearly movable rela tive to one another, the armature being an elongated member on which is wound a coil at least one part of which is energized with direct current through brushes on the field coil assembly, means connecting the movable part of the motor to said door and switches operative to wards each end of the door stroke to change the field current so as to slow the door down at each end of its travel.
2. A door operating mechanism as claimed in claim 1 wherein limit switches are provided operative at each end of the travel to interrupt the power supply to the field coil and armature winding.
3. A door operating mechanism as claimed in claim 1 wherein said switches operative towards each end of the door stroke are arranged to increase the field current and reduce the armature current over the last part of the stroke.
4. A door operating mechanism for giving linear motion to a door comprising a linear motor having an armature and a field coil assembly, the armature consisting of a bar of ferro-magnetic material with an electrically c0nductive coil wound around the bar but insulated therefrom and the field coil assembly being linearly movable relatively to said bar, said field coil assembly including brushes contacting the coil on the bar to feed direct current through a portion of the coil, a ferro-magnetic assembly which, with part of the bar, forms a magnetic circuit, at least one field coil fed with direct current for producing a flux in said magnetic circuit, the brushes being arranged to energize at least one part of the coil where the magnetic flux passes across the coil between UNITED STATES PATENTS 1,950,627 3/1934 Parvin 49-360 X 3,397,488 8/1968 Goldstein 49358 X FOREIGN PATENTS 1,031,409 6/1958 Germany.
805,223 12/1958 Great Britain.
1. KARL BELL, Primary Examiner US. Cl. X.R,