Contact block for pushbutton and rotary switch

Abstract

 The invention relates to an improved contact device suitable especially for use with manual control devices of the pushbutton and rotary types.
The contact devices comprises an insulating housing containing a contact structure, and terminal connectors extending from the contact structure outwardly of the housing through openings in wall portions thereof, wherein the terminal connectors (173) are substantially Z-shaped, and the housing has interior flanges (183) which, together with wall portions (162) of the housing adjacent the respective openings, define pockets in which intermediate portions (179) of the respective terminal connectors are lodged and retained, the flanges in addition serving as insulating barriers between the said intermediate portions of the terminal connectors and the contact structure (153,155,157).
The novel arrangement enables the component parts of the contact device to be mounted easily and without hardware, and it prevents electric flashovers or arcing from occurring between current-carrying parts disposed closely addcent each other.

Description

[0001] This invention relates generally to electric control switches and, more particularly, to an improved contact device suitable especially for use with manual control switches of the pushbutton and rotary types.

[0002] Many of the pushbutton and rotary type of control switches commonly employed nowadays as motor control devices consist of an operating unit including a manual operating member of the pushbutton and/or rotary type, and at least one contact device or contact block attached to the operating unit and operable thereby. Manufacturers of such switches are constantly striving to increase the controlling capabilities of their products, that is, to increase the number_' of circuits that can be served per switch, which usually means increasing the number of contact blocks attached to and operated by a given operating-. unit. Naturally, size is an important factor to be considered in the design of contact blocks to be used with control switches of this kind, it being apparent that the smaller the size the greater the number of contact blocks which can be combined with a given operating unit.

[0003] However, contact devices intended for use with electric control switches also need to be rugged and reliable, and in this respect miniaturization has been found to pose some problems, chief among them certain difficulties in mounting the internal component parts of such contact block securely in place with a minimum of hardware, and in preventing electric flashovers or arcing between conductive parts necessarily crowded closely together.

[0004] It is the principal object of the invention to alleviate these problems, and the invention accordingly resides in a contact device comprising an insulating housing defining a contact chamber therein, a contact structure disposed in said contact chamber and including contacts which are movable to closed and open position thereof through operation of the contact structure, an operating plunger for actuating the contact structure, and at least one pair of terminal connectors extending from the contact structure outwardly of the housing through openings in wall portions thereof, characterized in that each of said terminal connectors is a substantially Z-shaped member comprising an intermediate portion and contact-bearing and terminal portions extending in opposite directions with respect to each other from the opposite ends of said intermediate portion, and that said housing has disposed at each of said openings an interior flange which extends in substantially parallel spaced relationship with respect to the adjacent housing wall portion so as to define therewith a pocket having the intermediate portion of the associated terminal connector ; lodged and retained therein, said flange extending along- ; side said intermediate portion and forming an insulating barrier between the latter and said contact structure.

[0005] It will be appreciated that by the simple expedient of providing substantially Z-shaped terminal connectors and interior flanges cooperating with adjacent housing wall portions to form pockets in which to lodge the intermediate portions of the respective terminal connectors, the arrangement embodying the invention great facilitates the assembly of the contact device in that is enables the terminal connectors to be slipped in places simply by sliding their intermediate portions into the respective pockets, and, especially, results in a contact block having terminal connectors which (together with the stationary contacts on the contact-bearing portions thereof) are securely held in position by having their intermediate portions lodged and retained in the respective pockets, and wherein the same parts, viz, the interior flanges, which help to hold the terminal connectors in place also serve as insulating barriers effectively shieled- ing the closely spaced current-carrying parts of the contact structure and of the terminal conductors from one another.

[0006] The assembly of the contact device, the insulating housing of which preferably consists of two parts, can be further simplified by providing one of the two housing parts with the wall portions which cooperate with the internal flanges to define the pockets, and providing the other housing part with the flanges. This enables the terminal connectors to be readily inserted in their proper positions before the two housing parts are joined, and to be automatically and securely fixed in place when the housing part with the flanges thereon is placed upon and joined to the first-mentioned part.

[0007] A further object of the invention is to enable the contact device to be readily used in combination with another contact device or other contact devices of corresponding design, and accordingly it provides the housing of each such contact device with improved interlocking means, and preferably also with special screw receiving tubular portions, which will enable the various contact devices to be arranged and mechanically interlocked in tandem and/or in side-by-side relationship with respect to one another.

[0008] An embodiment of the invention will now be described, by way of example, with reference to the accom- panying drawings, in which:

Figure 1 is a vertical sectional view partly in elevation, of a switch utilizing two contact blocks according to the invention;

Fig. 2 is a horizontal sectional view taken on the line II-II of Fig. 1;

Fig. 3 is a horizontal sectional view taken on the line III-III of Fig. 1;

Fig. 4 is a horizontal sectional view taken on the line IV-IV of Fig. 1;

Fig. 5 is an exploded view of the operating unit of the switch;

Fig. 6 is a development showing the profile of the operating cam when the switch functions in two modes;

Fig. 7 is a development showing the profile of the cam when the switch functions in three modes;

Fig. 8 is a development showing the profile of the cam when the switch functions in four modes;

Figs. 9, 10 and 11 are elevational views of various legend plates with which the switch handle may be used;

Fig. 12 is a vertical sectional view part, elevation of another embodiment of the switch;

Fig. 13 is an exploded view of the opering parts of the switch shown in Fig. 12;

Fig. 14 is a horizontal sectional view tahen on the line XIV-XIV of Fig. 12;

Figs. 15 and 16 are alternate positions in pro- switch as shown in Fig. 14;

Figs. 17, 18, 19, and 20 are fragmentary vertical sectional views, partly in elevation, showing variets functions of the actuator;

Fig. 21 is a horizontal sectional view taken on the line XXI-XXI of Fig. 1;

Fig. 22 is an elevational view, with a portion broken away, showing two contact blocks according to the invention disposed side-by-side;

Fig. 23 is an end view taken on the line XXIII-XXIII of Fig. 22 and showing an additional upper contact block added in tandem; and

Fig. 24 is a horizontal view, partly in section and partly in elevation, taken on the line XXIV-XXIV or Fig. 23.

[0009] The switch generally designated in Fig. 1 with reference numeral 25 and shown as mounted on a panel 27 comprises an operating unit 29 and contact blocks 31, 33 arranged in tandenm. The operating unit 29 comprises a housing 35, a clamp ring 37, a handle or actuating knob 39, a contact actuator 41, a detent means or detent cam 43, and an operating cam 45. The housing 35 is a tubular member including a reduced portion 47 which extends through an aperture in the panel 27 and has a threaded end portion 49 on which the clamp ring 37 abutting the panel 27 is mounted and with which it is threadedly engaged, the clamp ring 37 being shown tightened so as, together with a shoulder 50 on the housing 35, to clamp the operating unit 29 securely in place on the panel 27. A legend plate 51 around the clamp ring 37 is disposed on the panel 27.

[0010] The handle 39 is composed of an electrically insulating material and preferably is translucent to transmit light from a light source or bulb 53. The handle 39 comprises a tubular portion 55 which is detachably mounted on the upper end of the contact actuator 41. As shown more particularly in Fig. 5, the tubular portion 55 comprises an end surface 57 and a pair of ears 59, 61 extending radially inward from the inner surface of the portion 55 and having end surfaces flush with the end surface 57. The ears 59, 61 are not diametrically opposed, the angular spacing or arc between them being greater on one side than on the other. In addition, the tubular portion 55 includes a first pair of outwardly extending stop ribs 63, 65 which project longitudrnilly beyond the end surface 57, and the angular spacing or circular are between which is greater on one side thereof than on the other. Finally, the tubular portion 55 includes a second pair of stop ribs 67, 69 which are wider than the ribs 63, 65, but which project from the end surface 57 the same distance 71 as the ribs 63, 65. The tubular portion 55 also has spaced notches 73 to permit contraction of the portion 55 as it is snapped into and out f place on the contact actuator 41 when repositioning the handle from one mode to another, as described later herein.

[0011] The contact actuator 41 (Fig. 5) has next to the handle 39 an annular portion which includes a radial flange 75 and, adjacent thereto, a pair of diametrically opposed cam detents 86, and it has axially extending from said annular portion a cylindrical splined portion consist- i_ng of a plurality of elongated segments or fingers 79 which are separated from each other through slots 77 and which have out-turned flanges 81 formed at the free ends thereof.

[0012] The-detent cam 43, which is annular, is slidably disposed on the splined portion of the contact actuator 41 and is resiliently held in engagement with the cam detents 86 by a spiral spring 83 (Fig. 1) disposed on the splined portion of the actuator 41 between the out-turned flanges 81 and the detent cam 43. The detent cam 43 has a plurality of notches 85 formed in the annular end face thereof which cooperates with the cam detents 86, and has formed in its peripheral surface two diametrically opposed guide grooves 87 in which there are slidably received a pair of longitudinal guide portions (see Figs. 1 to 4) formed on and projecting from the inner peripheral surface of the housing 35. The grooves 87 and the guide portions cooperate to guide the detent cam 43 for axial movement but to prevent rotational movement thereof.

[0013] As shown in Fig. 5, the annular portion of the contact actuator 41 has formed in the end thereof a plurality, such as three, notches 93, 95, 97 in two of which the ears 59, 61 of the handle 39 are engaged, depending upon whether the switch is to be operated in two, three or four modes or positions. For example, for operating the switch in two modes, the ears 59 and 61 would be disposed in the not-ches 95 and 97, respectively. For operating the switch in three modes, the ears 59 and 61 would be located in the notches 97 and 93, respectively. And for operating the switch in four modes, either ear 59 or 61 could be in the notch 93, 95 or 97 because, as explained below, the portions of the ribs 63. 65, 67, 69 corresponding to the distance 71 would be removed.

[0014] The manner of operating the switch in the two, three, and four modes is illustrated in Figs. 6, 7 and 8, respectively. In the two-mode operation, for which the handle 39 is mounted on the contact actuator 41 so that the ears 59 and 61 are engaged with the notches 95 and 97, respectively, the handle 39 is rotatable between two positions, namely, ON and OFF (see Fig. 9), as determined through the engagement of the stop rib 65 with the upper part of the guide portion 89 of the housing 35 occurring upon movement of the handle 39 from OFF to ON which causes the cam detents 86 to ride out of the respective notches 85a of the detent cam and into the notches 85b (see Fig. 6), and through the engagement of the stop ribs 63 with the upper part of the guide portion 89 occurring upon movement of the handle 39 from ON to OFF, which movement causes the cam detents 86 to ride out of the respective notches 85b and into the notches 85a.

[0015] For the three-mode operation, the handle 39 is repositioned on the actuator 41 so that the ears 59 and 61 become engaged with the notches 95 and 97, respectively, whereupon the handle is rotatable to three positions designated in Fig. 10 as HAND, OFF and AUTO. When the handle is in the OFF position, the detents 86 are in the respective notches 85b (Fig. 7) of the detent cam 43. Upon movement of the handle 39 from the off to the HAND position thereof, the detents 86 ride out of the associated notches 85b and into the notches 85a at which time the stop rib 67 will engage the upper end of the guide portion 89 and thereby arrest further rotation of the handle in the same direction, as indicated in solid lines in Fig. 7. If the handle 39 now is rotated from its HAND position to the AUTO position thereof, the detents 86 will ride out of the respective notches 85a, through the notches 85b, and into the notches 85c, whereupon the stop rib 69 will engage the upper end of the guide portion 89 and thereby arrest further rotation of the handle in the latter direction, as indicated in phantom lines in Fig. 7.

[0016] In order to condition the switch for a four-mode operation, all of the stop ribs 63, 65, 67, 69 are shortened to an extent corresponding to the dimension 71 indicated in Fig. 5. This will enable the stop ribs 63, 65, 67, 69 to clear the guide portion 89 of the housing upon rotation of the handle 39, as seen from Fig. 8, and thus will enable the handle 39 to be rotated to the four positions designated in Fig. 11 as ON, OFF, RUN and JOG, corresponding to the detents 86 being lodged in the associated notches 85a, 85b, 85c and 85d, respectively, of the detent cam 43. Rotation of the handle 39 beyond its ON position is prevented through engagement of one of the detents 86 with the guide portion 89 and of the other detent 86 with a projection 99 on the detent cam 43, as shown in solid lines in Fig. 8, whereas rotation of the handle 39 beyond the JOG position thereof is prevented through engagement of said one detent 86 with the projection 99 and of said other detent with the guide portions 89, as indicated in phantom lines in Fig. 8.

[0017] Referring now to Fig. 12, there is shown therein a modified switch 101 embodying the invention, reference numerals similar to those used in the preceding embodiment being employed to designate similar component parts of the switch 101. The operating unit 29 of the switch 101 shown in Fig. 12 includes a handle 103 which has a tubular portion 105 with a stop means comprising a longitudinal projection or flange 107 extending from adjacent one side of the tubular portion 105 in the axial direction thereof. A tab 109 (Fig. 13) projects from the periphery of the tubular portion 105 at a location which is spaced from a radial flange 111 at angles other than 180° so as not to be diametrically opposed thereto. The tab 109 preferably is provided with an index mark, such as an arrow 113. The reduced portion 47 of the housing 35 (Fig. 12) includes a pair of diametrically opposed guide portions 115 and 117 which are similar to the guide portions 89, 91 (Fig. 1), except that the guide portion 117 terminates in a lower surface 119 (Fig. 14) and an adjacent projection 121 extending up to the level of the end of the guide portion 115. The projection 121 has lateral stop surfaces 123 and 125 for limiting rotation of the handle 103.

[0018] The contact actuator 41 (Fig. 13) is provided with a plurality, such as three, tab-receiving notches 127, 129, 131, and with three slots 133, 135, 137, all formed in the end of the similar portion of the actuator. When the handle 103 is mounted on the actuator 41 so that its tab 109 is received in one of the notches 127, 129, 131, its radial flange 111 at the same time will be engaged with one of the slots 133, 135, 137. Thus, both the tab 109 and the flange 111 will transmit torque to the actuator 41 upon rotation of the handle 103. The mark 113 on the tab 109, together with mode-designating numerals provided on the bottom of the notches 127, 129, 131, assists in mounting the handle 103 on the actuator 41 in the desired position.

[0019] The manner of operating the switch 101 in the various modes will now be described with reference to Figs. 14, 15 and 16 in which the parts 107, 109, 111 are shown stippled, purely for contrast and not as a reference to any particular kind of material of which they are made. For two-mode operation (Fig. 14), the tab 109 is inserted into the notch 127 with the numeral "2", and the radial flange 111 in consequence will come to be placed into the slot 135, with the longitudinal projection or flange 107 extending adjacent a peripheral sector of the annular portion of the actuator 41. This will enable the handle 103 to be rotated between the OFF and ON positions shown in Fig. 9. In the OFF position, the parts are positioned as shown in solid lines in Fig. 14, i.e. with the detents 86 up against stop surfaces 125 and 141 on the guide portion 115 and on the projection 121, respectively. Movement of the handle 103 from the OFF position to the ON position will cause the parts to assume the positions appearing in Fig. 14 in phantom, i.e. it will cause the longitudinal flange 107 to strike the surface 139 of the guide portion 115 and thereby arrest movement of the handle and contact actuator 41 in the ON position.

[0020] For three-mode operation (Fig. 15), the handle 103 is placed upon the actuator 41 so that the tab 109 is in the notch 129 with the numeral "3", and the radial flange 111 is in the slot 133. This will enable the handle 103, and consequently, the actuator 41 to be moved in 45° steps to OFF, HAND and AUTO positions. When, as shown in solid lines in Fig. 15, the detents 86 are up against the stop surfaces 125 and 141, respectively, the handle 103 is in its HAND position. Rotation of the handle 103 in two 45° increments (determined by the spacing of the notches 85'in the detent cam 43) from the HAND position first to the OFF and then on to the AUTO position will bring the longitudinal flange 107 up against the stop surface 123 cf the projection 121, as shown in phantom in Fig. 15, which will arrest further rotation of the handle in this direction. It will be noticed that the flange 107, in moving toward the projection 121, clears the recessed or lower surface 119 of the guide portion 117.

[0021] In order to prepare the operating, unit 29 for four-mode operation (Fig. 16), it is necessary to remove, e.g. cut away, a portion 143 of the flange 107 along the broken line 145 seen in Fig. 13; along this line 45, the flange 107 may be reduced in thickness, e.g. notched, to facilitate removal of the portion 143. The handle 103 is then mounted on the actuator 41 so that the tab 109 is engaged with the notch 131 marked "4", and the radial flange 111 is engaged with the slot 137, whereupon the handle can be rotated in 45° increments to four positions, such as the positions ON, OFF, RUN and JOG shown in Fig. 11, since the portion 143 was removed and, hence, no longer interferes with the projection 121, and movement of the handle together with the actuator 41 consequently is limited only by the guide portions 115 and 117 when engaged by the detents 86 upon movement of the handle to either the ON or the JOG position.

[0022] Rotation of the operating unit 29 of either switch 25 (Fig. 1) or switch 101 (Fig. 12) results in a corresponding rotation of the operating cam 45 which, in turn, actuates the contact blocks 31, 32 and 33, as described hereinafter. The contact blocks, which may be arranged in tandem, as seen from Fig. 1 or 12, or side-by-side, as shown in Figs. 17 to 22, arc of similar construction, each comprising, as shown particularly in Figs. 22 and 24, a pair of stationary contacts 155, a bridging contact carrier 157 carrying two movable contacts 153 and in turn supported on an operating plunger 149 or 151 in a conventional manner, such as shown in U.S. Patent No. 3,919,506, so as to provide a normally open (as shown) or a normally closed contact condition, having regard to the position toward which the plunger together with the bridging contact carrier thereon is biased by a spring (not shown). The stationary contacts 155 and the bridging contact carrier 157 together with the movable contacts 153 thereon are disposed in a contact chamber 159 (see Fig. 24) formed in an insulating housing which comprises opposite side walls 161, 162, opposite end walls 165, 167, and top and bottom walls 169, 171. The plunger 149 or 151 extends movably through an opening in the top wall 169. To facilitate assembly, the side wall 161 and the end walls 165, 167 are formed integral with each other to constitute a cover, and the side wall 162 and the top and bottom walls 169, 171 are formed integral with each other to constitute a base, the base and the cover being joined together in a suitable manner, preferably by welding.

[0023] As shown in Fig. 22, each of the stationary contacts 155 is mounted on a generally Z-shaped terminal connector 173 comprising an inner or contact bearing portion 175, an outer or terminal portion 177, and an intermediate portion 179. The outer portion 177 carries a terminal-screw-and-clamp assembly 181 enabling an external conductor (not shown), such as a stranded wire, to be connected thereto.

[0024] As seen best from Fig. 22, the intermediate portion 179 is disposed between the side wall 162 of the housing and a wall portion or flange 183 which extends inwardly of the latter end and has a surface 185 opposite the side wall 164 substantially equally spaced from the latter a distance substantially equal to the thickness of the intermediate portion 179. The wall portion 183 is formed of an electrically insulating material, and preferably is molded integral with the housing from the same material, such as a clear thermoplastic. The wall portion or flange 183 serves as an insulating barrier preventing electric arcs, such as may occur between the contacts 153 and 155, from jumping onto the intermediate portion 179 of the terminal connector; thus, it facilitates the extinction of such arcs.

[0025] The terminal connectors 173 seated in the pockets thus formed between the side wall 162 and the respective barriers 183 are retained in their proper positions without the use of additional hardware when the housing base and cover are assembled.

[0026] The housings of the various contact blocks 31, 32, 33 are provided with integral means, including prongs 187 and recesses 189, which fit together to retain the blocks in tandem relationship with respect to each other, as shown in Fig. 23. Likewise as shown in Fig. 23 and also in Fig. 24, the blocks are provided in addition with tubular housing portions 191 having countersunk openings 193 extending therethrough and designed too for receiving screws 195 each of which comprises a threaded stem 197 and a head 199 having a threaded axial bore 203 formed therein. Each screw 195 is inserted into the associated opening 193 so that its head 199 rests against the shoulder 201 within the opening, and its stem^-197 extends completely through the latter to be threadedly engaged with the threaded bore 203 of a similar, axially aligned screw 195 used in an adjacent tandem-connected contact block, if any, or if the respective contact block adjoins directly the operating unit 29, to be used in securing the contact block to the latter, such as by threadedly engaging the screws 195 with openings (not shown) formed in the lower side of the housing 35 of the operating unit 29.

[0027] If several contact blocks, such as 31, 32 and 33, are arranged in two stacks, with the blocks in each stack secured together in tandem and with the two stacks arranged side-by-side and secured to the operating unit 29, as shown in Fig. 24, the forces applied by the screws 195 along parallel lines near the outer faces of the two stacks of tandem-connected contact blocks may tend to pull the two stacks apart at some distance from where they are secured to the operating unit 29. In order to prevent such separation between the two stacks of tandem-connected contact blocks, the housings of the latter are also provided with interconnecting means, such as cooperating hooks 205, 207, extending from the side wall 161 of each contact block and engaged with the corresponding hooks of the adjacent block so as to hold the blocks of the two stacks together, as seen from Fig. 24 , as well as properly aliened with the operating unit 29.

[0028] The manner in which the operating cam 45 is mounted on the lower end of the contact actuator 41 and how it cooperates with the plunger of the contact blocks 31, 32 is shown in Figs. 17-20. The cam 45 is an annular member having cam surfaces 209, 211 (Fig. 1) and mounting spokes 213 (Fig. 5) extending radially inward of the annular member and spaced apart to fit slidably into the respective slots 77 of the contact actuator 41, as seen from Figs. 17-20. Thus, when the contact actuator 41 is rotated, the cam 45 rotates with it to actuate one or both plungers 149. 151 by virtue of its cam surfaces 209, 211. as shown in Fig. 17. However, if the handle 39 or 103 is operated as a pushbutton instead of as a rotary type of switch actuator, the contact actuator 41 is moved in the direction of the arrow 215 (Fig. 18) to depress both plungers 149, 151, while the operating cam; 45 is allowed to remain in its position due to its sliding connection with the actuator 41 formed by the spokes 213 and the stop 77. As seen from Fig. 21, the upper ends of the plungers 149. 151 overlap with both the cam surfaces of the operating cam 45 and the flanges 81 at the lower ends of the longitudinal actuator segments 79 so that the plungers 149, 151 are acted upon by the segments 79 of the actuator as well as by the cam surfaces 209, 211 of the cam 45. If desired, one or more of the longitudinal segments 79 may be eliminated, as shown in Fig. 19 in order to disable the contact actuator 41 to the extent that, when depressed, it will not actuate one of the plungers, i.e. plunger 149 in Fig. 19, while actuating the other.

Claims

1. A contact device comprising an insulating housing defining a contact chamber therein, a contact structure disposed in said contact chamber and including contacts which are movable to closed and open position thereof through operation of the contact structure, an operating plunger for actuating the contact structure, and at least one pair of terminal connectors extending from the contact structure outwardly of the housing through openings in wall portions thereof, characterized in thai each of said terminal connectors (173) is a substantially Z-shaped member comprising an intermediate portion (179) and contact-bearing and terminal portions (175, 177 extending in opposite directions with respect to each other from the opposite ends of said intermediate portion, and that said housing has disposed at each of said openings an interior flange (183) which extends in substantially parallel spaced relationship with respect to the adjacent housing wall portion (162) so as to define therewith a pocket having the intermediate portion of the associated terminal connector lodged and retained therein, said flange (183) extending alongside said intermediate portion (179) and forming an insulating barrier between the latter and said contact. structure; (153, 155, 157).

2. A contact device according to claim 1 wherein said insulating housing consists of two parts joined together, characterized in that one of said parts includes the housing wall portions (162) adjacent the intermediate portions (179) of said terminal connectors, and the other of said parts has the pocket-defining and barrier-forming flanges (183) disposed thereon.

3. A contact device according to claim 1 or 2, characterized in that said insulating housing includes external interlocking means (187, 189) enabling the contact device to be separably joined together in tandem with an additional, corresponding contact device.

4. A contact device according to claim 3 and including a screw for fastening the switching device together with said additional corresponding contact device, characterized in that said screw (195) has a head (199) with a threaded bore (203) axially formed therein, and said insulating housing Includes an external tubular portion (191) for receiving said screw, said tubular portion extending axially parallel with respect to said plunger (149 or 151) and containing an annular shoulder (201) forming a seat for the head of the screw, and the latter being threadedly engageable with the threaded bore in the head of a corresponding screw disposed in a corresponding tubular portion of the additional contact device.

5. A contact device according to claim 3 or 4, characterized in that said interlocking means are hooks (187) and hook-receiving recesses (189).

6. A contact device according to claim 1, 2, 3, 4 or 5, characterized in that said insulating housing includes external interlocking means (205, 207) enabling the contact device to be mechanically interlocked in side-by-side relationship with another, corresponding contact device.

7. A contact device substantially as hereinbefore described with reference to. and as illustrated in. Figs. 1, 12 22, 23 and 24 of the accompanying drawings.

Drawing