Patent GB-520185-A (GB)
Title: Improvements relating to switch machines for railway points
IPC: B61L5/06
Filed: 1938-10-11
Abstract: 520,185. Electric operation of railway points. BOOT, J., and GENERAL RAILWAY SIGNAL CO., Ltd. Oct. 11, 1938, No. 29474. [Class 104 (i)] An electric control system for a number of inter-related points, as at a crossing T3, comprises a control station C, separate electric motors Ma, Mb for the various points A, B controlled from the station C, and means whereby, at the end of each operation, the motors are brought to rest' by snubbing or dynamic braking circuits, one of said circuits extending to the station C, and means for indicating at the station that the snubbing circuits have been established, said indication being given by alternating current from a separate circuit l<SP>1</SP>, l<SP>2</SP> induced from one to another of the'snubbing circuits in a sequence ending at the snubbing circuit which extends to the station C. The motor Ma for the point A has a pole changer comprising two rows of fixed controls c<SP>1</SP>... c<SP>6</SP>, c<SP>54</SP>, c<SP>55</SP> and c<SP>7</SP>...c<SP>12</SP>, c<SP>57</SP>, c<SP>58</SP>, and movable bridging contacts c<SP>13</SP>...c<SP>15</SP>, c<SP>56</SP>. When point A is at or near normal, the bridging contacts are as shown, but if at reverse, they bridge the contacts c<SP>1</SP> ... c<SP>6</SP>, c<SP>54</SP>, c<SP>55</SP>. The motor Ma includes a point detector operated by the point and comprising two rows of fixed contacts c<SP>26</SP>...c<SP>29</SP> and c<SP>30</SP>...c<SP>33</SP>, and movable bridging contacts c<SP>34</SP>, c<SP>35</SP>, which are in position shown when point A is at normal, and on c<SP>30</SP> or c<SP>33</SP> when point is at reverse. The detector comprises also contacts c<SP>36</SP>, c<SP>37</SP> which engage only when point is at full normal, and contacts c<SP>50</SP>, c<SP>51</SP> which engage when point is at reverse. The machine Mb has a pole changer with two rows of fixed contacts c<SP>16</SP>...<SP>19</SP> and c<SP>20</SP>...c<SP>23</SP>, alternately bridged by movable contacts c<SP>24</SP>, c<SP>25</SP>. Its point detector comprises two rows of fixed contacts c<SP>38</SP>...c<SP>41</SP> and c<SP>42</SP>... c<SP>45</SP>, bridged alternately by movable contacts c<SP>46</SP>, c<SP>47</SP>. The detector comprises also contacts c<SP>48</SP>, c<SP>49</SP> which engage when point is at full normal, and contacts c<SP>52</SP>, c<SP>53</SP> which engage at full reverse. The station C contains normal and reverse relays Nw, Rw controlling contacts N<SP>1</SP>, R<SP>1</SP>, and an A.C. relay having a field winding ar and a local winding across A.C. and lines l<SP>1</SP>, P. A transformer p<SP>1</SP>, s<SP>1</SP> is associated with Ma, and another p<SP>2</SP>, s<SP>2</SP> with Mb. When points are at. normal as shown, a snubbing circuit is formed for Ma through s<SP>1</SP> and ar, and one for Mb through p<SP>1</SP>, and s<SP>2</SP>. An A.C. circuit is also formed from l<SP>1</SP>, l<SP>2</SP> through p<SP>2</SP>, inducing an A.C. current by transformer p<SP>2</SP>, s<SP>2</SP> in the snubbing circuit of Mb. and an A.C. current is induced by p<SP>1</SP>, s<SP>1</SP> in the snubbing circuit of Ma and in ar. The A.C. relay at C then indicates that both snubbing circuits are formed and that points are at normal. When point A is to be reversed, R<SP>1</SP> is engaged with R<SP>3</SP> and a D.C. current from L<SP>1</SP>, L<SP>2</SP> drives Ma to reverse the point. Just before the point reaches reverse, the pole changer of Ma moves to reverse, breaking the circuit of Ma, and forming both a reverse snubbing circuit for Ma and a D.C. circuit for Mb to move point B to reverse. Just before B point reaches reverse, the pole changer of Mb moves to reverse, breaking Mb circuit, and forming reverse snubbing circuit for Mb. As both point detectors have reached reverse, p<SP>1</SP> is connected across l<SP>1</SP>, l<SP>2</SP>, so that an A.C. current is induced by p<SP>2</SP>, s<SP>2</SP> in the snubbing circuit of Mb and thence by p<SP>1</SP>, s<SP>1</SP> in the snubbing circuit of Ma and in ar, giving a reverse indication at C.