MXPA96004408A - Programmer / timer program - Google Patents

Abstract

The present invention relates to an electromechanical timer / timer, comprising: (a) housing means having a motor associated therewith; (b) cam means mounted for rotation about an axis in said housing means and having a rotary registration surface and a plurality of cam rails therein; (c) advance means operatively connected to said engine and effective to sequentially advance said cam means; (d) plate means having a first portion thereof defining a first surface in contact with said registration surface of the cam means, said plate means having second portions integrally formed therein that define a plurality of spaced, resilient cam followers; (e) a plurality of switches associated with said housing means, each of said switches arranged for actuation by one of said followers, and (f) operating clutch means. Rables when the user moves in the direction of said axis to disable said cam followers to allow rotation of said cam means without causing actuation of any of said switch

Description

PROGRAMMABLE PROGRAMMER / TIMER BACKGROUND OF THE INVENTION The present invention relates to programmers / timers of the type having a plurality of switches operated in a timed sequence to control the operation of the various functions of an electrical appliance. Programmers / timers of this kind are typically employed to control the program cycle of household appliances such as clothes washers and automatic dishwashers. Such programmers / timers for dishwashers and clothes washers commonly employ a program cam, which is advanced in timed relation, for example by means of a feed mechanism driven by a timing motor of a small fractional horsepower to sequentially drive the various function switches. In the aforementioned time-based programmers / timers for clothes washers and dishwashers, the cam is commonly configured as a rotating drum which is initially positioned to select the length of the program by rotation by the user of a knob attached to it. the arrow on which the cam is mounted. In an arrangement widely used in particular for clothes washers and dishwashers, the knob is arranged to be pushed or pulled in the axial direction to allow rotation and set the program cam when knob movement occurs in an axial direction and the energization of the programmer / timer by movement in the opposite axial direction. Users have become accustomed to this mode of operation control and has achieved widespread acceptance in the home appliance market. Up to now, in the design and manufacture of programmers / timers for household appliances, problems have been encountered in locating and arranging the cam followers for precise, timed sequencing for the operation of the various switches. The tolerances accumulated in the manufacture of the cam, the placement of the cam for rotation in the housing or base of the programmer / timer, and the tolerances in the manufacture of the individual cam followers and the placement of the followers in the base or programmer / timer housing, have made it difficult to achieve the desired program precision with a cam drum sized to adjust the volume envelope available to the timer / timer. Furthermore, the tolerances accumulated in the manufacture of the individual components and the assembly of the advancing mechanism have caused inaccuracies in the advancement in cam increments by the advance mechanism, which in turn results in greater timing inaccuracies. of the switches. In this way, in designing and manufacturing electromechanical programmers / timers for household appliances, and particularly those employing a plurality of switches operated by an advanced cam sequentially, the problem of placing the program cam with respect to the switches has been formidable, in view of the tolerance accumulation of the parts and the fact that more than one reference data is used to place the cam followers and switches with respect to the cam. Therefore, for a long time it has been desired to provide a simplified construction for an electromechanical timer / timer that eliminates the inaccuracies due to the accumulation of tolerance when placing the switches with respect to the program cam. Furthermore, in the aforementioned type of programmer / timer for electromechanical devices where a single pole, double shot (SPDT) interruption is required for each switch, it has been found quite difficult to control the accuracy of the interruption of the lateral contacts where a rotating cam is used to drive the cam followers and switches. Where a cam drum employs a single cam track for each switch, it has been found to be difficult to provide the precise formation and rupture of the lateral contact with the single cam track. Up to now, in such a programmer / timer type, and particularly where an SPDT interrupting action is desired, only the central or common contact has been moved to achieve the interruption of the lateral contacts. This has resulted in certain inaccuracies of the interruption, which it has been desired to eliminate. Hitherto, programmers / timers of the aforementioned type have employed a plurality of cam rails on a cylindrical surface to form a cam drum against which a switch cam follower travels on each of the several cam rails formed around it. of the drum. In this type of interruption arrangement, in order for an SPDT switch to work, the central or common blade must follow the movement of the cam follower and thus slide against the friction of the cam ramp, or up the cam , to effect the closing of one of the side contacts with the common contact blade, upon occurrence of which the precision of the interruption is a function of the spacing of the lateral contact from the common contact blade. The amount of cam movement and time in this manner are determined by the limit of the slope of the ramp. Where a revolution of the cam drum represents a complete or total program cycle of the domestic appliance, this necessarily limits the frequency of the actuation of the switch that can be obtained for a given size or diameter of the cam drum, for a given rate of advance. Of cam. In addition, electromechanical programmers / timers known for household appliances, particularly those used for clothes washers and dishwashers that employ a plurality of switches operated by a rotating cam, have exhibited the undesirable characteristic of being noisy when the user moves the knob axially to rotate the cam to select the starting position and the time of the program interval. This is because, when turning the cam, the followers are moved to mechanically activate and deactivate the switches despite the electrically de-energized state of the programmer / timer. In this way, it has also been desired to provide an inexpensive way to de-link the cam from the followers to eliminate the noise of actuation and deactivation of the switch during the setting of the program cam by the user. In this way, it has long been desired to provide a design for an electromechanical device programmer / timer that eliminates the above disadvantages and limitations. Essence of the Invention It is an object of the present invention to provide an electromechanical timer / timer having a plurality of sequentially operated cam-operated switches, and to minimize inaccuracies in sequence timing caused by tolerance accumulations when placing trackers. Cam with respect to the cam.

It is an object of the present invention to provide an electromechanical timer / timer for a household appliance having a plurality of household appliance function switches sequentially actuated and deactivated by motorized advancement of a cam. It is another object of the present invention to provide a timer / programmer for household appliances in which the rotatable cam is moved out of engagement with the cam followers by the axial movement of a user control knob attached to the arrow of the cam. It is another object of the present invention to provide an electromechanical, cam-operated programmer / timer for home appliances in which movement by the user of the control knob in one direction moves an arrow to link the program cam with the followers of cam and detaches the arrow from the cam to prevent its rotation by rotating the user's control knob. It is another object of the present invention to provide an electromechanical programmer / timer having cam-operated switches of the single-pole, double-throw type, where the side contacts of each switch are closed by a fall action of the cam follower on the cam . It is another object of the present invention to provide a plurality of household appliance function control switches operated by the advancement of a rotating cam and to improve the timing accuracy of the switch drive and reduce the relative costs of manufacturing the programmer / timer. . The present invention provides an electromechanical timer / timer for household appliances of the type employing a cam disk capable of rotating with a plurality of cam ks provided on the axial face of the disk which, upon advancement of the cam, performs actuation and Sequential deactivation, by means of appropriate individual cam followers, of a plurality of household appliance function control switches. The programmer / timer of the present invention employs a motor driven feed mechanism in the form of a spring loaded feed ratchet which operates against rack teeth provided on the periphery of the cam disk. The cam followers are formed integrally on a plate as a plurality of resiliently deflectable fingers having plastic tips molded thereon, which tips each follow a cam k on one side of the disc. The movement of the advancing ratchet is limited by contacting a stationary portion of the plate, thereby minimizing the effect of the accumulation of tolerances on the cam position with respect to the cam followers. Upon the occurrence of the assembly of the invention during manufacture, the plate is recorded against a hub portion of the cam disc, which also minimizes the accumulation of tolerances and thereby improves the accuracy of positioning of the cam followers relative to the cam followers. Cam rails on the disc. The cam disc of the present invention is movable axially towards or away from the cam followers by means of the movement of the user of a control knob mounted on an arrow. A clutch mechanism links the arrow to the cam when cam movement occurs away from the cam followers to allow rotation of the cam by the user to select a desired program interval with cam followers disengaged from the cam. The movement of the arrow by the user in the opposite axial direction disengages the clutch to prevent rotation of the cam by the user and links the cam disk with cam followers for actuating switches. The advancement of the cam in increments by the ratchet contact with the rack teeth is limited by a limit stop on the follower plate, which provides a reference to the cam followers. The contact of the molded plastic tips on each cam follower with the stationary portion of the follower plate prevents contact of the cam followers with the cam rails when the cam disk is reted by the movement of the arrow by the user to link the clutch clutch and the rotation of the cam disk.

Brief Description of the Drawings Figure 1 is an exploded view of the programmers / timers of the present invention; Figure 2 is a cross-sectional view of the invention of assembled Figure 1, with the cam disk retracted from the cam followers; Figure 3 is a view similar to Figure 2, with the cam disk linking the cam followers; Figure 4 is an axonometric view of the follower cam plate of the invention of Figure 1; Figure 5 is an enlarged detail of the advance pawl and the cam rack of the embodiment of Figure 1; Figure 6 is an enlarged detail of one of the cam followers and switch assemblies of the embodiment of Figure 1; Figure 7 is a schematic of a switch of the present invention, with the central contact blade dropped to close the lower contact assembly; Figure 8 is a schematic of the switch of the figure 7, with the lower contact blade dropped to open the lower contact assembly; Figure 9 is a schematic of the switch of Figure 7 before dropping the central contact blade; Fig. 10 is a schematic similar to Fig. 7, showing the cam moved from the position of Fig. 7 to re-close the lower set of contacts; Figure 11 is a diagram of the switch of Figure 7, with the cam positioned to drop the upper and lower contact arms to close the upper contact assembly; Figure 12 is a diagram of the switch of Figure 11, with the central contact arm dropped to open the upper contact assembly; Figure 13 is a diagram of the switch of the figure 11 with the cam moved to a position immediately before dropping the upper contact blade arm; and Figure 14 is a diagram of the switch of Figure 11, with the upper contact arm dropped to re-close the upper contact assembly. Detailed Description Referring to Figures 1, 2 and 3, the programmer / timer of the present invention is generally indicated at 10 as having a shell or housing 12 closed by a cover plate 14 and has a timing motor transmission indicated generally at 16 which preferably includes a synchronous timing motor and speed reducing gears to drive an arrow or output hub 18 to operate a feed mechanism generally indicated at 20.

Disc-shaped cam means, generally indicated at 22, are rotatably mounted around the arrow 24, which is received in a clutch hub 26 which is muted through an aperture 28 in the case 12. The media followers Cam members generally indicated at 30 include a plate member 32, which defines a plurality of cam followers, as will be described hereinafter, and which has an aperture 34 formed therein which is rotatably recorded against a hub surface. small diameter 36 provided in the hub 35 of the disc 22. A plurality of switch contact blade members, generally indicated at 38 and 39, are mounted in the housing for actuation by the cam followers, as will be described later with more detail. With reference to Figure 1, it will be understood that the plurality of switch contact blades 38, 39 are individually molded into insulating blocks denoted by the reference numerals 41, 43, 45. Referring to Figures 1 and 5, the plate 32 has a limit stop 40 there formed which is operative to limit the displacement or advancement in cam increments. The feed mechanism 20 includes a feed pawl 42 driven by an eccentric gear 44 which links an anvil 46 formed in the pawl 42. Preferably, a sub-range cam wheel 48 is provided for rotation with the eccentric gear 44 and allows the activation of a sub-interval interruption function. The cam disk 22 has a double row of peripheral rack teeth denoted by the reference numbers 5052 formed peripherally around it, the row 50 having a radius higher or thinner than the row of teeth 52. A second advance pawl 54 is provided on the opposite side of the sub-interval cam 48 from the ratchet 42 and is guided by the ratchet 42 by means of a pin formed in the pawl 42, which links a pin 58 in the pawl 54 formed adjacent the free end of the pawl.

Referring to Figure 5, the pawl 42 has a groove 60 formed therein that is engaged by a pin 62 extending from the pawl 54 to align the pawl 54 and the pawl 42 during advancement. In the presently preferred practice, the pawl 54 performs a faster rate of advancement by virtue of the circumferentially stacked teeth 50, 52 and the limit stop 40 engaging only the rack teeth of finer radius 50. When it is desired to have the teeth operative 50 of slower advancement, it will be understood that a segment of the teeth 52 will be left lacking to render the forward ratchet 54 inoperative. Referring to FIG. 1, a sub-interval switch actuator 62 links the sub cam. -intervalue 48 and is guided to oscillate by the slots 64 provided in the plate 32, which are linked by suitable nipples 66 provided in the actuator 62. The actuator 62 links a sub-interval switch as will be described in greater detail as successive. Referring to Figure 5, a resilient arm 67 is formed in the plate 32 and has a stop 40 molded thereon so as to link the teeth 50 on the slow feed rack. The stop 40 has a tooth generally in the form of a bevel 47 dependent thereon, which connects the teeth 50 of the rack. When the rack is advanced by the driving ratchet, the arm 67 is biased to allow the point 47 of the stop 40 to travel over the teeth 50 and fall between the teeth 50 to function as an anti-reverse stop for the rack during retraction of the impulse ratchet. During the forward momentum movement of the ratchet 42, the stop 40 limits the movement of the ratchet. Referring to Figures 1, 2 and 3, the cam disk 22 has a plurality of concentric cam rails 68 formed on its face to effect actuation of the switches as will be described below. Referring to Figure 4, plate 32 has a plurality of resilient teeth denoted by reference numerals 70, 76 therein formed, which are arranged in a parallel arrangement, generally spaced, each having its free end provided with a follower molded plastic provided thereon with track follower surfaces, as denoted by the reference numerals 72, 74, 75 in Figure 4. Referring to Figures 4 and 6, it will be understood that each of the molded tips having the follower surfaces denoted by the reference number 74 is integrally molded therein a secondary lower level follower, one of which is visible in Figure 4 and is denoted by the reference number 75. The cam followers 70 with their tips have follower surfaces 72, 74, 75, and are disposed on the plate 32 so as to be placed on a generally common radial station of the cam disk 22, each one for connecting the cam rails 68, 69. A second set of cam followers denoted by the reference number 76 is formed on the plate 32 on the opposite side of the aperture 34 as the follower 70; and the followers 76 each have a plastic tip molded on them having follower surfaces as denoted by the reference numbers 78, 79, 80 in Figure 4. Referring to Figure 4, each of the arms Cam followers 76 having the molded tip with follower cam surfaces 78 also have a lower level cam follower surface 79 provided therein.

Each of the molded tips with follower surfaces 72, 74, 78, 80 has its end provided with a tongue respectively denoted by reference numerals 82, 84, 86, 88 which extend over the edge of the cutout or recess from which they are formed. the resilient followers 70, 76 on the plate 32, such that the tabs 82, 84, 86, 88 make contact with the surface of the plate 32 to limit the deflection or travel of the resilient followers. It will be understood that the tips molded into the follower arms 76 make contact with the cam rails 68., 69 in a generally common radial station diametrically opposite from the tips 72, 74. With reference to figures 1 and 6, the plurality of switches 38, 39 are respectively arranged for driving by the molded tips on the arms 70, 76, where each of the switches comprises a central, upper and lower contact blade in SPDT arrangement, as is typically denoted for one of the switches by reference numerals 90, 92, 94. Referring to Figures 1, 2 and 3, the cam disk 22 has radially spaced, concentric rails 68, formed as raised rails of the disk face; and the spaces between the raised rails 68 comprise the second set of concentric, radially spaced cam rails 69 which are generally coincident with the face of the disc, as illustrated in Figures 2 and 3. It will be understood that adjacent, alternating follower arms 70. 76 have the molded tips formed to respectively link the cam rails 68, 69 in order to maximize the number of switches in the groups of switches 38, 39 that can be driven by the single cam disc 22. Referring to the figure 6, a typical double-throw, single-pole switch assembly, comprising the blades 90, 92, 94, is shown as driven by a pair of cam followers, typically the follower surfaces 74, 75 at a tip and the follower surface 72 on an adjacent arm. With reference to figures 4 and 6, the follower surface 75 is shown as making contact with the lower contact blade 94; the high level follower surface 74 contacting the lower surface of the upper contact blade 90; while the follower surface 72 of an adjacent follower arm 70 makes contact with the lower surface of the central contact blade arm 92. The follower tip including the follower cam surfaces 74, 75 is integrally molded therewith a dependent rail denoted by reference numeral 96. The adjacent molded follower arm tip having cam follower surface 72 therein integrally molded with it is a deep, dependent rail follower 98. It will be understood that track follower 96 typically links one of the cam rails 68, while the deep rail follower 98 links one of the cam rails 69. Referring to Figures 7 to 10, a typical switch forming the group comprising the plurality of switches 38 is shown schematically as driven by the movement of adjacent cam rails 68, 69. Referring to Figure 7, the switch is shown in the condition where the cam track follower 98 has been lifted by the cam track 69 to a position that causes the follower surfaces 76 to raise the lower switch blade 94 while the cam track surface 74 raises the upper switch blade 90. Simultaneously, the cam track follower 96 has been allowed to fall down the cam track 68 causing the follower cam surface 72 to drop to the central contact blade. 92, thereby making contact between the contact blade 92 and the blade 94. Referring to Fig. 8, the switch of Fig. 7 is shown in the condition in which the cam rail 69 has advanced sufficiently to allow the follower of rail 98 fall to the same level as rail 68, thus causing the follower surfaces 75 and 74 to fall, at which occurrence the follower surface 75 lowers the contact blade 94 sufficient This is to maintain contact with the blade 92, which is maintained by the follower surface 72 with the blade 90 held on the blade 92 by the follower surface 74. Referring to Figure 9, the cam rails 68, 69 have been advanced from the position shown in Figure 8 to a position that raises the track followers 96 and 98, thereby raising the follower surfaces 75, 72, 74 and raising the blades 94, 92, 90 while maintaining their relative positions of all the blade contacts being in the open position. Referring to Figure 10, the cam disc 22 has been further advanced from the position shown in Figure 9 to a position similar to that of Figure 7, where the cam track 68 has caused the 96 track follower to fall. , thereby enabling the contact blade 92 to make contact with the blade 94, thereby again closing the lower switch of the SPDT arrangement. Referring to figure 11, a switch of the present invention is shown having the cam track follower 96 lowered by the cam track 68, thus causing the follower surface 75 to lower the blade 94 and the follower surface 74 to the lower blade 90. Simultaneously, the cam track 69 has caused the follower 98 to rise, causing the follower surface 72 to raise the blade 92 to make contact with the upper blade 90, thus closing the upper switch of the SPDT arrangement. Referring to Figure 12, the cam disk 22 has been advanced from the position shown in Figure 11 to a position where the cam follower 98 has been dropped by the cam track 69 with the rail 68 maintaining the follower 96 in the lowered position, resulting in the fall of the central blade 92 to break the contact with the upper blade 90, which is maintained by the follower surface 74. Referring to Figure 13, the cam disk 22 has been advanced further from the position of Figure 12 to a position where the cam rails 68, 69 have lifted both track followers 96, 98 to a position that maintains the relative open position of the contact blade arms relative to each other, as illustrated in figure 12, that is, both upper and lower contact arms are separated from the central contact arm 92. With reference to figure 14, the cam disk 22 has been further advanced from the position shown in Figure 13 to a position where the cam track 68 has dropped the follower 96, thus lowering the follower surfaces 75 and 74 to lower the blade 94 and similarly lower the upper blade 90. Simultaneously, the cam track 69 has been advanced to a position that holds the rail follower 98 in a raised position where the cam surface 72 and the contact blade 92 can be reclosed with the upper contact 90, thus returning to close the upper breaker of the SPDT arrangement. . In this way, it will be seen from the above descriptions with respect to Figures 7 to 14, that both the upper and lower blade contact switches of the SPDT arrangement are actuated to close when a cam fall action occurs, which improves the accuracy of the interruption and provides a faster closing of the respective switches. With reference to Figures 1, 2 and 3, a further aspect of the invention is illustrated where a circular flange or disk on the center 100, having a double beveled periphery, is rigidly attached to the arrow 24 for movement therewith and includes a plurality of dog clutch teeth 102 engaging corresponding dog clutch teeth 104 formed within the hub 35 of the cam disk 22. A generally U-shaped spring member 106 is provided on the bottom surface of the disk 22 and is linked by the outer periphery of the flange 100 upon axial movement of the arrow to provide an action of elastic action to the cam disk 22 upon axial movement of the arrow 24. With reference to FIG. 2, the arrow 24 is shown moved towards the upward position, whereby the largest diameter of the flange member 100 has passed through the spring 106, causing the bevelled surface of the flange at 100 move the cam disk 22 downwardly relative to the flange, causing the dog clutch teeth 102 of the flange to link the dog clutch teeth 104 to the hub 35. It will be understood that when the cam disk 22 is moved to the descending position shown in Figure 2, the cam rails 68, 69 are disengaged from the cam followers 96, 98, allowing the cam disk to be freely rotated by the rotation of the arrow 24 by the user without turning the disc 22 and without causing any of the cam rails to drive any of the switches 38, 39. This arrangement, therefore, allows the user to move the arrow to the position inward of the housing 12 and rotate the disc of cam 22 for initial positioning to establish the starting position of the switches 38, 39 relative to the cam rails 68, 69 and then re-link the cam followers with the cam disk 22 when the knob is pulled out. With reference to Figure 3, the arrow 24 has been moved down or out of the housing 12 by the movement of the user, such that the flange 100 has passed downwardly through the spring 106, causing the flange to move the disc cam 22 upwards to a position that disengages the clutch teeth 104 from the clutch teeth 102 and by linking the cam track 68 with the cam followers for the switches 39 and link the track followers for the switches 38 with the track rail. cam 69. It will be understood that with the arrow and flange in the position shown in figure 3, the arrow 24 is freely able to rotate inside the cam disk; and the cam disk is linked to the impulse ratchet 42, 54 which connects the rack teeth 50, 52 and the cam is advanced by operation of the advancing mechanism.

Referring to Fig. 1, it will be understood that the sub-interval switch actuator 62 is operative to link one of the tabs 86, 88 in the plurality of cam followers 76 to provide a sub-interval interrupt drive for the respective selected switch associated with the particular cam follower 76. Although the invention has been described hereinabove with respect to the illustrated embodiments, it will be understood that the invention is capable of modification and variation and is only limited by the scope of the following claims.

Claims (21)

1. CLAIMS 1. An electromechanical timer / programmer, comprising: (a) accommodation means having a motor associated with them; (b) cam means mounted for rotation about an axis in said housing means; (c) advance means operably connected to said engine and effective to sequentially advance said cam means; (d) plate means having certain portions thereof recorded in said cam means, said plate means having other portions integrally formed with a plurality of resilient, spaced cam followers; (e) a plurality of blade switches associated with said housing means, each of said switches arranged for actuation by one of said followers, and (f) clutch means operable upon the user's movement in the direction of said axis for disabling said cam followers to allow rotation of said cam means without causing any of said switches to actuate. The programmer / timer defined in claim 1, wherein said cam means includes a disk with a plurality of cam rails, at least one of said cam followers arranged to follow each cam track. 3. The programmer / timer defined in claim 1, wherein said advancing means comprises a rack and an oscillating ratchet that drives said rack. The programmer / timer defined in claim 1, wherein at least one of said switches comprises a single-pole, double-throw switch, and said cam means and follower means are operable to effect a fall to make and fall to break the drive for both side contacts of said switch of a single pole, double shot. The programmer / timer defined in claim 1, wherein said plate means includes a plurality of resilient metal fingers, generally parallel, spaced, with plastic tips molded therein, said tips comprising said cam followers. The programmer / timer defined in claim 1, wherein said plate means includes stop means operable to limit the advancement of said cam means. The programmer / timer defined in claim 1, wherein said plate means is registered in said cam means on a surface concentric with the axis of rotation of said cam means. The programmer / timer defined in claim 1, wherein said advancing means includes a rack wheel having a first set of rack teeth for advancement at a first speed and a second set of rack teeth having a greater slope than said first set for advancing at a second higher speed, with predetermined intervals without teeth, and said advancing means includes a first ratchet linking said first set of teeth and a second ratchet linking said second set of teeth, wherein said wheel is made advancing at said first speed during said predetermined intervals without teeth. The programmer / timer defined in claim 1, wherein said plate-plate cam followers each have a tip molded thereon, said operating tips each to contact said plate means to limit the movement of said followers. The programmer / timer defined in claim 1, wherein said cam means is mounted on an arrow and includes clutch means operable upon movement of said arrow by the user in an axial direction to detach said cam means from said means followers and to allow the rotation of said cam means by means of the rotation of said arrow means by the user, said clutch means operable to link said cam means with said follower means upon subsequent movement of said means of arrow by the user in the opposite axial direction and to allow free rotation of said arrow means with respect to said cam means. 11. The programmer / timer defined in claim 10, wherein said clutch means includes spring means on the center. The timer / programmer defined in claim 12, wherein said clutch means includes a chimed connection between said arrow means and said cam means. The programmer / timer defined in claim 1, wherein said plate means includes a limit stop for said advance means. The programmer / timer defined in claim 1, wherein said plate means includes anti-reverse means for said advancing means. 15. A method of making an electromechanical timer / timer, comprising: (a) forming a rotating cam and rotatingly arranging it on a base; (b) arranging a motorized advance mechanism on said base and sequentially advancing said cam; (c) forming a plurality of resilient cam followers, spaced, integrally on a common member and registering said member against a surface of said cam; and (d) providing an individual switch on said base for actuation by each of said cam followers. The method defined in claim 15, wherein said step of registering said member includes forming a cutout in said member and registering its edge in a hub portion of said cam. The method defined in claim 15, wherein said step of forming cam followers includes forming a plurality of fingers integrally in a metal plate and molding plastic over the tips of said fingers. The method defined in claim 15, further comprising providing a clutch member operated by the user and moving said member in the direction of the cam rotation axis and detaching said cam from said followers. The method defined in claim 15, wherein said step of sequentially advancing said cam includes oscillating a ratchet against a rack wheel and arranging a limit stop for said ratchet on said common member. The method defined in claim 15, wherein said step of advancing said cam includes disposing a rack wheel with a set of coarsely inclined teeth, with missing tooth spaces and a set of fine tilt teeth arranged concentrically with said teeth of coarse inclination and oscillating a first ratchet against said set of coarsely inclined teeth and oscillating a second ratchet against said fine inclined teeth when said first ratchet is against said missing tooth spaces. The method defined in claim 15, wherein said step of forming a plurality of cam followers includes forming a plurality of fingers and molding a plastic tip on each finger and contacting said plate with said tip and limiting the movement of said finger. finger.