US2810435A

US2810435A - Timing mechanism

Info

Publication number: US2810435A
Application number: US448623A
Authority: US
Inventors: Roy C Demi; Wantz Clarence
Original assignee: Robertshaw Fulton Controls Co
Current assignee: Robertshaw Controls Co
Priority date: 1954-08-09
Filing date: 1954-08-09
Publication date: 1957-10-22
Anticipated expiration: 1974-10-22

Description

Oct. 22, 1957 R. c. DEMI ETAL TIMING MECHANISM 4 Sheets-Sheet 1 Filed Aug. 9. 1954 dz. Y wm/ m Wa M w V Q@ me@ M ap/g d mm WU m Nm Rw wm mw QN E wm NN uw u a mw ww Q1 S Sv Nw. Alm. wmm vh -V S ww \\\\A. @u Mm Mw ww mw mm f bh NN QM mm www m uw sm ww NQ @N @N www ct. 22, 1957 R. c. DEMI ET AL 2,810,435

TIMING MECHANISM INVENToRs Hog C. 27eme and By Clave/26e Wzzz.

THEIR TTEVFY Oat. 22, 1957 R. C. DEMI I'AL TIMING MECHANISM Filed Aug. 9, 1954 FoJozz/ep 529 F060wep 60 mf HelicaZ Surface 65 4 Sheets-Sheet 4 JNVENTORS Roy U. enu' and BY lal'ence Wanz. MM

THEIR TTORNEY nited States Patent O sie TIMING MECHANISM Roy C. Demi, Greensburg, Pa., and Clarence Wantz, Los

Angeles, Calif.; said Demi assignor to Robertshaw- Fulton Controls Company, Greensburg, Pa., a corporation of Delaware Appiication August 9, 1954, Serial No. 448,623

' 9 Claims. (cl. 161-1) This invention relates generally to control devices for mechanical movements and more particularly to novel latching and tripping mechanisms.

It is a principal object of this invention to control, through mechanical means, a relatively large operating force by the application of a relatively small control force.

Another object of this invention is to utilize a relatively small control force to control a relatively large operating force which may vary in magnitude without affecting th required control force.

Another object of this invention is to utilize the friction between coacting detent elements to balance the effects of an operating force being controlled, thereby permitting the elements to be moved relative to each other through the application of a relatively small force.

Another object of this invention is to utilize a mechanical escapement mechanism of a relatively fragile construction to control relatively large forces.

This invention finds particular utility in the application of escapement type clock movements to the control of elements subjected to relatively heavy loads. In escapement devices, the power available for control purposes is equal to the difference between the power necessary to keep the escapement movement running and the power which causes the escapement movement to overbank. As a result of the allowance of the usual manufacturing tolerances, the actual power available in most movements is considerably less than the theoretical power available and in some instances this power is minute.

It is an object of this invention to utilize this available power for con-trolling relatively large operating forces of varying magnitudes.

in a preferred embodiment of the invention, an axially loaded control member carries a pair of abutment means engageable respectively with a pair of helical surfaces for holding the control member within a predetermined range of axial positions. The helix angles of the helical surfaces are such that the axial load on the control member Itends to move one of the abutment means along its associated helical surface while at the same time producing, between the other abutment means and its associated helical surface, frictional forces tending to resist such movement. Thus, the tendency toward slidable movement is substantially balanced by the frictional resistance to such movement and the application of a slight torque will permit rotation of the control member regardless of the axial load thereon. are provided with relieved portions for the reception ,of the abutment means in a selected angular position of the control member to permit axial movement of the control member for performing a control operation.

Other objects and advantages will appear from the following specification taken in connection with the `accompanying drawings wherein:

Fig. 1 is a sectional view of a valve device with an actuating mechanism therefor embodying this invention;

Fig. 2 is a side elevation cf the device shown in Fig. 1;

Preferably, the helical surfaces` Patented Oct. 22, 1957 ICC Fig. 3 is a sectional view of a detail on an enlarged scale;

Fig. 4 is a perspective view of a detail on anfenlarged scale;

Fig. 5 is a fragmentary sectional view taken on the line V-V of Fig. 1 and shown on an enlarged scale;

Fig. 6 is a fragmentary sectional view taken on the line Vl-VI of Fig. l with portions of the apparatus removed for the sake of clarity and shown on an enlarged scale;

Fig. 7 is a fragmentary view on a greatly enlarged scale of a portion of the device shown in Fig. 1 with a vector diagram superimposed thereon; and

Fig. 8 isa fragmentary view on a greatly enlarged scale of another portion of the device shown in Fig. 1 with a vector diagram superimposed thereon.

Referring more particularly to the drawings, the control device is shown as applied to a valve of the type utilized to control ow of fuel to tiuid fuel burners. The valve comprises a casing 10 provided With a valve chamber 12 which is adapted to be connected to a source (not shown) of fluid fuel through an inlet 14 and to a fluid fuel burner (not shown) through an outlet passage 16. A tapered valve seat 18 is formed on the casing 10 in the valve chamber 12 and is engaged by the seating surface of a plug valve member 20.

The plug valve member 20 is provided with an angular passage 21 comprising an axial passage and a communicating radial inlet passage 22 adapted to register with the inlet passage 14 in the casing 10 in one angular position of the plug valve member 20. The angular passage 21' in the plug valve member 20 is also provided with an outlet 24 which communicates with the valve chamber 12 in all positions of the plug valve member 20.

As is customary in gas cocks of this type, rotation of the plug valve member 20 to place the inlet 22 of the angular passage in registry with the casing inlet 14 or with the seating surface of the valve seat 18 will respectively permit or prevent fluid flow to the valve chamber 12 and outlet passage 16.

One end of the plug valve member 20 forms a valve stem 25 which extends out of the casing 10 and which is adapted to receive a handle or knob to be more fully described hereinafter. Acting between the plug valve member 20 and a suitable retainer 124 secured to the lcasing 10 is a spring Z6 which acts to bias the valve member 2t) against the tapered seat 18 and insure a fluidtight seal therebetween.

The wall of the angular passage 21 is chamfered at the outlet end 24 to form an annular valve seat 30. A poppet-type valve member 32 is positioned adjacent the valve seat 30 and is movable into and out of engagement therewith to control fluid ow through the angular passage 21 in the valve member 20. The valve member 32 is mounted on one end of a valve stem 34 which extends through an axial bore 36 formed in the plug valve member 20 and stem 25, the other end 38 of the valve stem 34 extending out of the plug valve member 20 and terminating adjacent the end of the plug valve stem Z5. Bottomed in a counterbore 40 formed in the plug valve stem 25 coaxial with the bore 36, is a spring 42 which bears n against a collar 44 secured to the valve stem 34 to bias the valve member 32 toward the valve seat 30.

Means is provided for operating the plug valve member 20 between open and closed positions. This means is here shown as comprising a manually operable unit having a hub 46 secured to the end of the plug valve member which extends from the casing 10. A radially extending flange 48 is formed on the hub 46 and a cup-shaped housing 50 is secured to the ange 48 by anysuitable means such as screws 52. The housing 50 thus constitutes a knob .which may be manually lmanipulated to rotate the plug valve member between open and closed positions, rotation of `the housing 50 being effective to rotate `the plug valve member and move the inlet l22 of the angular passage 21 in the plug valveV member 20 1nto and out of registry with the inlet passage 14 formed in the casing 10.

Means for moving the valve member 32 relative to the valve seat Sti is provided and is here shown as including a movable element operatively connected to the valve stem 34. The movable element comprises a shaft -54 which extends slidably through the housing 50 and is recessed at one end to loosely receive the end of a plunger 126. The plunger 126 extends slidably through `the hub 46 along the axis of the valve stem 34 extended and is engageable with the end 38 of the valve stem 34. The shaft 54 is free to rotate and move axially relative tothe housing 50. Secured to 'the end of lthe shaft 54 which extends out of the housing 50 is a manually operable knob 56 for imparting such movements to the shaft 54. The spring 42 biases the valve stem 34 into operative engagement with the shaft 54 through the plunger 126 'to urge the shaft 54V out of the housing SG and the shaft 54 may be moved against such bias to move the valve member 32 away from the valve seat by manual manipulation of the knob 56. Suitable indicia 57, indicating units of time, are imprinted on the edge of the knob for registry with a reference mark S9 on the housing 50 for a purpose which will more fully appear hereinafter.

Secured to the inner end of the shaft 54 is a plate 5S which carries a pair of oppositely disposed abutment means or followers which take the form of

projections

58, 60 extending from the plate 5S and disposed parallel to the axis of the shaft 54. The follower 58 is positioned Y slightly farther from the axis of the shaft 54 than is the follower 60 for a purpose which will more fully appear hereinafter.

A relatively stationary detent member is engageable with the

projections

58, 60 for preventing axial movement of the shaft 54 and comprises a generally annular cam assembly 64 secured to the inside of the housing 50. The cam assembly 64 includes a radial flange 65 which is adapted to be seated in a suitable recess 61 formed in the housing Si). The ange 65 is retained in the recess 61 by a plate 62 which underlies the flange 65 and is secured to the housing 50 by screws 53.

An annular body portion extends axially from the flange 65 with the end portion thereof being shaped to detine a first helical surface'V 66; The helical surface 66 extends through approximately 350 with. the' high and low extremities thereof separated by a relieved portion or recess 67 which extends parallel to the axis of the shaft 54 and is adapted to receive the projection 58 of the plate 55. Coaxial with and positioned radially inward of the helical surface 66 is a second helical surface 68 which extends through approximately 350 with the high and low extremities thereof being separated by a relieved portion or recess 69. The recess 69 is substantially di'- ametrically opposed to the recess 67 and is adapted to receive the projection 60 of the plate 55.

Preferably, each helical surface 66, 68- terminates in a portion 70, v71 disposed normal to the axis of the' cam assembly 64 to provide a manual setting as will more fully appear.

The` lead of the helical surface 66 is the same as the lead of the helical surface 68. However, since the helical surface 66 is disposed radially outward of the helical surface 68, it will be -apparent that the helix angle of the former will be smaller thanl the helix angle of the latter. This differential inhelix angles constitutes ,an important feature of the invention as will more fully appear hereinafter. Y

The shaft 54 extends slidably and rotatably through the open center of the annular cam assemblyv 64 so xthat axial movement of the shaft 54 in one direction is limited by engagement of the

followers

58, 60 with the cam assembly 64.

The length of the valve stem 34 is such that, when the followers 58, 6l) are positioned within the

recesses

67, 69, the spring 42 will hold the valve element 32 in its biased or closed position in engagement with the valve seat 30. However, when the shaft S4 is moved axially to move the followers 5S, 66 out of the

recesses

67, 69, the valve stem 34 is moved against the bias of the spring 42 to space the valve element 32 from the valve seat 30, thereby permitting fuel flow through the angular passage 21 in the plug Valve member 20. lf the shaft S4 is rotated after it has moved Athe valve element 32 to open position, the

followers

58, 60 will engage the

helical surfaces

66, 68 and the valve element 32 will be retained in its open position.

It will be apparent that the axial thrust exerted on the valve stern 34 by the spring 42 will be transmitted directly to the shaft S4 and

tothe followers

58, 60 carried thereby. Since the

helical surfaces

66, 68 are disposed at an angle to the line of action of this force, a portion of the force will be transformed to torque and will tend to rotate the shaft 54 with accompanying slidable movement of `the

followers

58, 60 down the helical surfaces 66, 63. However, the

helical surfaces

66, 68 will exert a reactive force on the

followers

58, 60, a portion of which will comprise a torsional component acting in a direction to resist such sliding action of the followers S8, 60.

It is an important feature of this invention that the coacting surfaces of the followers 5S, 60 andthe relatively stationary cam assembly 64 be so arranged that the operating force acting upon the movable member 54 will produce acomponent of force substantially equal in magnitude and opposite in direction to the reactive component of force resulting from friction between such surfaces regardless of the magnitude of the operating force. With such an arrangement, an extremely small force may be utilized to disengage the movable element 54 from the stationary or detent element 64.

This principle may be more fully explained by reference to Figs. 7 and 8 which show respectively contacting portions' of the follower 5S and helical surface 66 and contacting portions of the follower 60 and helical surface 68 Ywith Vector diagrams of the forces involved superimposed thereon;

Referring -to Fig. 7, the vector L represents the load on the follower 58 resulting from the axial thrust on the shaft 54 exerted by the spring 42 when the

followers

58, 60 are in engagement with the

helical surfaces

66, 68. This force L acts along a line parallel with the common axis of the valve stem 34 and the shaft 54 and produces aV reactive force exerted by the helical surface 66, such reactive force being equal in magnitude and opposite in direction to the force L. This reaction is represented by the vector R in the vector diagram.

Since the force L does not act normal to the surface 66, it produces a component of force acting parallel to .the same which tends to move the follower 58 along the helical surface 66. This force is represented by the vector Lm ink the vector diagram. The force L will, of course, createy another component of force acting normal to the surface 66. This force is represented by the vector Lp in the vector diagram. p

. SinceLp is normal to the helical surface 66, and L is parallelY with the axis of the helical surface 66, the angle a included between these vectorsY is equal to the helix angle of the helicalA surface 66, the helix angle being the angle which the helical bearing surface makes with a plane perpendicular to the axis thereof'. Thus, the magnitudeof the force Lm will equal Lp times the tangent of angle a or` timesV the tangent of the' helix angle of the helical surface 66. i

The reactive force exerted by theA helical surface 66 may also be resolved into two components parallel and normal to the helical surface respectively. These components are represented in the vector diagram by the vectors Rf and Rp respectively. The force Rp will, of course, be equal in magnitude to the force Lp. The force represented by the vector Rf will be the resistive force resulting from friction between the follower 58 and surface 66 and will be dependent upon the magnitude of the component Rp and the coeiicient of friction of the engaging surfaces. The resistive force Rf will resist relative sliding movement between the follower 58 and the surface 66.

It is desirable that the resistive force Rr be greater than the force Lm so that the force Rf will inhibit slidable movement between the follower 58 and the helical surface 66. In other Words, Rf must be greater than Rp times the tangent of angle a and, accordingly, the angle a or helix angle, will determine the degree to which slidable movement is inhibited since it determines the magnitude of the force Lm. Accordingly, the helical surface 66 is formed with a relatively small helix angle selected to produce the desired resistance to slidable movement, the magnitude of which will be equal to the difference between the magnitude of the forces Rf and Lm.

Referring now to the vector diagram of Fig. 8, the vector L represents the axial thrust on the follower 60 resulting from the axial thrust on the shaft 54 exerted by the spring 42 when the

followers

58, 60 are in engagement with the

helical surfaces

66, 68. This force act-s parallel to the common axis of the valve stem 34 and shaft 54 and produces a reactive force exerted by the helical surface 68, such reactive force being equal in magnitude and opposite in direction to the operating force L. This reaction is represented by the vector R.

Since the force L' does not act normal to the helical surface 68, it produces a component of force acting parallel to the surface 68 which tends to slide the follower 60 along the helical surface 68. This force is represented by vector Lm' in the vector diagram.

The force L will, of course, create another component of force acting normal to the surface 68. This component is represented by the vector Lp'.

Since Lp is normal to the helical surface 68 and L is parallel with the axis of the helical surface 68, the angle a included between these vectors is equal to the helix angle of the helical surface 68. Thus, the magnitude of the force Lm' will equal Lp times the tangent of angle a or Lp' times the tangent of the helix angle of the helical surface 68.

The reactive force exerted by the helical surface 68 may also be resolved into two components parallel and normal to the surface 68 respectively. These components are represented in the vector diagram by the vectors Rr and Rp respectively. The force Rp will, of course, be equal to the force Lp. The force represented by the vector Rf will be the resistive force resulting from friction between the follower 60 and the helical surface 68 and will be dependent upon the magnitude of the component Rp and the coefficient of friction of the engaging surfaces of the follower 60 and the helical surface 68. The resistive force Rf will resist relative sliding movement between the follower 60 and the helical surface 68.

Preferably, the force Lm is greater than the force Rr in order to create a tendency for the follower 60 to slide along the helical surface 68 under the axial thru-st on the shaft 54. Therefore, Rp' times the tangent of angle a' must be greater than Rf', and for a given material having a predetermined coefficient of friction, the helix angle of the helical surface 68 will determine the degree of the tendency toward slidable movement of the follower 60 along the helical surface 68. Accordingly, the helical surface 68 is formed with a relatively large helix angle so that the force Lm is always greater than the force Rf and the resultant force tending to impart slidable 'I5 The housing 50 nis first manually manipulated to rotate` movement to the follower 60 will be equal to the dilferen'ce between the magnitude of the forces Lm and Rf.

From the foregoing, it will be apparent that the total torque acting on the shaft 54 as a result of the axial load thereon will be determined by the summation of the tendency toward slidable movement produced by engagement of the follower 60 with the helical surface 68 and the tendency to resist slidable movement produced by engagement of the follower 58 with the helical surface 66. In a preferred embodiment of the invention, the helix angles of the

helical surfaces

66, 68 are selected to produce a balanced condition with the moment exerted on the shaft S4 by the follower 58 being substantially balanced by the moment exerted on the shaft 54 by the follower 60. Thus, rotation of the shaft 54 may be effected by the application thereto of a relatively small torque without regard to the magnitude of the axial thrust on the shaft 54. Y

Means is provided for applying a control force to the valve actuating means to effect release of the movable operating member 54 from the detent member 64. This means takes the form of an escapement controlled clock movement 80. The movement is disposed within the housing 50 and is carried on the ange 48 by a plurality of screws 82.

The movement 80 includes a main spring assembly 84 geared to an escapement mechanism 86 through a suitable gear train 88. The main spring assembly 84 is best shown in Fig. 3 and comprises a pintle 90 non-rotatably secured to the flange 48 and extending normal to the plane thereof. A spirally wound spring 92 is secured at its inner end to the pintle and lies in a plane substantially parallel to the flange 48. A cup-shaped element 94 encompasses the spring 92 and is carried by a gear wheel 96 rotatably mounted on the pintle 90. The outer end of the spiral spring 92 is secured to the element 94 at 98 so that rotation of the gear 96 and cup-shaped element 94 will vary the tension of the spring 92.

A second gear 100 is rotatably mounted on the pintle 90 and carries an axially extending ange 102 which frictionally engages the cylindrical wall of the cup-shaped element 94. This it is preferably such that africtional torque will be developed between the tlange 102 and the element 94 which will always be greater than the maximum torque developed by the main spring 92 when the same is completely wound. A plurality of slots 104 (only one of which isl shown) may be formed in the flange 102 to facilitate manufacture and avoid the necessity of extremely close tolerances in fitting the flange 102 over the cup-shaped element 94. Y

The gear meshes with a suitable gear in the gea train 88 and thus is directly connected to the escapement mechanism 86. The gear 96 meshes with a pinion 106 which is loosely mounted on the plunger 126 and connected to the shaft 54. The connection between the pinion 106 and the shaft 54 is such that the shaft 54 may move axially relative to the pinion 106 while a torque transmitting relation is maintained therebetween. This connection is here shown as comprising a first leaf spring 108 secured at its medial portion to the pinion 106 and a second leaf spring 110 secured at its medial portion to the plate 55 which is secured to the end of the shaft 54. The juxtaposed ends of the leaf springs 108, 110 are riveted together at 112 so that rotational movement will be transmitted between the pinion 106 and the shaft 54 but, upon axial movement of the shaft S4, the springs 108, 110 will flex, causing no axial displacement of the pinion 106.

Operation Assuming that the control device is in the olf position with the plug valve member 20 and poppet valve member 32 in closed positions, the various parts may be placed in operating condition as follows:

the plug valve member 20 and bring the inlet 22 of the angular passage 21 into registry with the inlet passage 14 of the casing 10. The variousparts of the apparatus are then in the position shown in Fig. 1 and fluid may ow from the inlet 14 into the angular passage 21, outow therefrom being prevented by the valve member 32.

The knob 56 is then depressed to move the shaft 54 axially, carrying the

followers

58, 60 out of the

recesses

67, 69, where rotation thereof is prevented, and axially beyond the lower extremities of the

helical surfaces

66, 68. Such movement of the shaft 54 will impart axial movement to the valve stem 34, moving the same against the bias of the spring 42 and positioning the valve element 32 away from the valve seat 30. Fluid may then flow past the valve member 32 to the outlet 16 of the casing 10.

The knob 56 is then rotated in a clockwise direction, as viewed in Fig. 2, to a desired time setting indicated by the indicia 57 and the reference point 59. Rotational movement of the knob S6 rotates the shaft 54 to move the

followers

58, 60 into engagement with the

helical surfaces

66, 68. As hereinbefore pointed out, the helix angles of the

helical surfaces

66, 68 are such that the tendency toward rotational movement of the shaft 54 is balanced by the frictional force resisting such movement. The shaft 54 will therefore remain in the position in which it has been set unless an additional torque is applied thereto to start rotation of the same and move the

followers

58, 60 down the helical` surfaces 66, 68 toward the recesses 67 69.

it will be understood that the sequence of the rotational setting movements of the housing 50 and the knob S6 may be reversed if desired with setting of the timer knob 56 preceding operation of the valve member 20 by the housing 50.

The rotational setting movement of the knob 56 also rotates the pinion 106 which drives the gear 96 and winds the mainspring 92 of the clock movement 80. The gear 108 tends to rotate with the gear 96 because of the frictional connection therebetween but it is prevented from doing so by the timer gear train 88 and escapement 86. Slippage therefore ocurs between the

gears

96 and 100. However, when the knob 56 is released, the torque of the mainspring 92 is transmitted directly to the gear 96 and frictionally to the gear 100. Since the frictional torque between

gears

96 and 100 is greater than the maximum torque of the mainspring 92, the mainspring torque will cause common rotation of the

gears

96 and 100 as a unit. This rotation of

gears

96 and 100 will dn've the gear train 88 and the pinion 106, the escapement 86 controlling the speed of rotation and the pinion 106 causing return rotation of the shaft 54 and knob S6 to their initial angular positions.

When the mainspring 92 has rotated the shaft 54 to its initial angular position, the

followers

58, 60 are disengaged from the

helical surfaces

66, 68 and, since the

followers

58, 60 are then aligned with the

recesses

67, 69, the shaft 54 will be moved rapidly to the right as viewed in Fig. 1 until the

followers

58, 60 engage the bottoms of the

recesses

67, 69. Simultaneously with this axial movement of the shaft 54, the valve member 32 will move into engagement with its seat 30 with a snap-action to prevent further flow of fluid to the outlet 16 of the casing 10.

When the

followers

58, 60 move into the

recesses

67, 69, further rotation of the shaft S4 is prevented. The clock movement 80 will then stall and further unwinding of the mainspring 92 is prevented. Thus, the manspring 92 will never be permitted to run down and a substantial torque may be exerted thereby on the shaft S4 in all angular positions of the shaft 54 to eliminate any danger of insuicient Winding of the mainsprng 92 when the timerV is set to operate at a small time interval. p

It is to be noted that since the

followers

58, 60 are diametrically opposed to each other, they will engage and disengage the

helical surfaces

66, 68 simultaneously thereby preventingpossible tilting and binding of the shaft 54.

if it is desiredV to eliminate control of lluid ow by the timer 80, the knob S6 is depressed to move the

followers

58, 60 to a position beyond the higher extremities of the

helical surfaces

66, 68 and the knob is then rotated in a direction opposite to the time setting direction to place the

followers

58, 60 in engagement with the surfaces '70, 71 which are disposed in a plane normal to the axis of the shaft 54. Any operation of the clock movement will then tend to force the follower 58 into engagement with a stop 72 which extends from the surface 70 and the shaft 54 will be maintained in its depressed position, thereby holding the valve element 32 away from its seat 30.

It will be apparent that the hereinbefore described apparatus includes a novel detent mechanism wherein an operating force of considerable magnitude may be applied to a movable member and movement of such member under the inuence of the operating force may be controlled by an extremely small control force. The detent mechanism comprises the

followers

53, 60 and the

helical surfaces

66, 68, the helix angles of the

helical surfaces

66, 68 being selected to produce equal and opposite torsional Ycomponents of any axial thrust imposed upon the shaft 54.

Accordingly, it will be apparent that the illustrated embodiment provides a new and improved control device and accomplishes the objects of the invention. It will also be obvious to those skilled in the art that the illustrated embodiment may be variously changed and modified, or features thereof, singly or collectively embodied in other #combinations than those illustrated without departing from the scope of the invention or sacrificing all of the advantages thereof, and that accordingly the disclosure herein is illustrative only and the invention is not limited thereto. t

It is claimed and desired to secure by Letters Patent:

l. In a control device, the combination comprising a member having one side thereof defining a plurality of helical surfaces and a relieved portion, a second member including abutment means frictionally engageable with said surfaces and adapted to be received in said relieved portion, said members being axially movable and rotatable relative to each other, means for exerting a force on one of said members for moving the same into engagement with the other of said members, means for im parting axial and rotational movement to one of said members to separate said abutment means from said relieved portion and' place the former in engagement with said surfaces respectively, and actuating means for rotating said one member to impart slidable movement to said abutment means relative to said surfaces to return said abutment means to said relieved portion, said helical surfaces being inclined at different predetermined angles respectively to render the frictional engagement of said abutment means therewith eective to produce a resistive force tending to prevent said slidable movement and an equal force tending to produce said slidable movement in response to the rotative force of said actuating means.

2. In a control device, the combination comprising a member having a pair of coaxial helical surfaces on one side thereof, each of said surfaces being provided with a relieved portion, a second member including a pair of abutment means respectively engageable with said surfaces and adapted to be received in said relieved portions, said members being axially movable and rotatable relative to each other, means for biasing said members into engagement with each other, means for imparting axial and rotational movement to one of said members to separate said abutment means from said relieved portions and place the former in engagement with said surfaces respectively, and actuating means for rotating said one member to impart slidable movement to said e abutmentrmeans relative to said surfaces to return said abutment means to said relieved portions, one of said helical surfaces being formed with the helix angle tending to produce relative motion between Said members under said bias when said abutment means are in engagement with said surfaces, the other of said surfaces being formed with the helix angle tending to inhibit relative rotation between said members under said bias when said abutment means are in engagement with said surfaces and substantially balance forces tending to produce said relative rotation.

3. A control device as claimed in claim 2 wherein Said actuating means comprises a timing device operatively connected to said one member.

4. In a controldevice, the combination comprising a member having a pair of coaxial helical surfaces on one side thereof, each of said surfaces being provided with a relieved portion, a second member having a pair of abutment means respectively engageable with said surfaces and adapted to be received in said relieved portions, a shaft secured to one of said members and movable relative to the other of said members, means for biasing said abutment means toward said surfaces, manually operable means for imparting axial and rotational movement to said shaft for moving said abutment means away from said relieved portions and positioning said abutment means in engagement with said surfaces respectively, and actuating means for rotating said shaft to impart slidable movement to said abutment means relative to said surfaces to return said abutment means to said relieved portions, one of said helical surfaces being formed with a helix angle tending to produce relative rotation between said member and said shaft under said bias when said abutment means are in engagement with said surfaces, the other of said surfaces being formed with a helix angle tending to inhibit relative rotation between said member and said shaft under said bias when said abutment means are in engagement with said surfaces and substantially balance forces tending to produce said relative rotation.

5. A control device as claimed in claim 4 wherein said actuating means comprises a timing device operatively connected to said shaft.

6. In a control device, the combination comprising control means movable between a plurality of positions and biased to one of said positions, a shaft operatively connected to said control means and axially movable to move said control means against said bias to another of said positions, means defining a pair of concentric helical cam surfaces coaxial with said shaft, each of said cam surfaces being provided with a relieved portion, abutment means movable with said shaft and engageable with said surfaces for moving said control means i-n said other position, and actuating means for rotating said shaft for imparting slidable movement to said abutment means relative to said surfaces to move said abutment means into registry with said relieved portions and permit said control means to move under said bias to one said position, one of said helical surfaces being formed with a helix angle tending to produce relative rotation between said shaft and said surfaces under said bias when Said abutmentl means are in engagement with said surfaces, the other of said surfaces being formed with a helix angle tending to inhibit relative rotation between said shaft and said surfaces under said bias when said abutment means are in engagement with said surfaces and substantially balance forces tending to produce said relative rotation.

7. A lcontrol device as claimed in claim 6, wherein said actuating means comprises an escapement control timing mechanism operatively connected to said shaft.

8. In a control device, the combination comprising control means movable between a plurality of positions and biased to one of said positions, a shaft operatively connected to said control means and axially movable to move said control means against said bias to another of said positions, means defining a pair of concentric helical cam surfaces coaxial with said shaft, each of said cam surfaces being provided with an axially extending recess, a pair of followers movable with said shaft and extending axially thereof, said followers being constructed and arranged to be received in said recesses for locating said shaft in a iirst axial position wherein said control meansis in said one position, a handle secured to said shaft for imparting axial movement thereto to move said followers out of said recesses and position said control means in another of said positions, said handle being operable for imparting rotational movement to said shaftv and positioning said followers in engagement with said surfaces to hold said control means in said other position, and actuating means for rotating said shaft for imparting slidable movement' to said followers relative to said surfaces to move said followers into registry with said recesses and permit said control means to move under said bias to said one position, one of said helical surfaces being formed with a helix angle tending to produce relative rotation between said member under said bias when said abutment means are in engagement with said surfaces, the other of said helical surfaces being formed with a helix angle tending to inhibit relative rotation between said shaft and said surfaces underrsaid bias when said abutment means are in engagement with said surfaces and substantially balance forces tending to produce said relative rotation.

9. A control device as claimed in claim 8 wherein said actuating means comprises an escapement control timing mechanism operatively connected to said shaft.

References Cited in the le of this patent UNITED STATES PATENTS 382,654 Montgomery May 8, 1888 2,454,887 Schott Nov. 30, 1948 2,592,024 Goodroad et al. Apr. 8, 1952 2,641,437 Jay et al. June 9, 1953