Patent Publication Number: US-3880534-A

Title: Molded control knob

Description:
United States Patent Schmidt Apr. 29, 1975 MOLDED CONTROL KNOB 331 L393 3/l967 Leitmann 292/353 x 3. 9.252 7 9 2 .7 3 3 [75] lnvenm Schmidh Chmg 3289.531 1/l9i3 i [73] ASSigIICCZ Bell 8L &#34;0W8&#34; Company, ChlCtlgO. FOREIGN PATENTS OR APPLICATIONS l 040 838 W66 United Kingdom l6/l2l [22] Filed: June 25, l973 Primary Iiruminer-James T. McCall [2]] Appl&#39; 373&#39;l66 Assistant [:Iramincr-William E. Lyddane Allurney. Agent. or Firm-Roger M. Fitz-Gerald; John [52] US. Cl. .l 403/230: l6/l2l; 74/553: R. Hoffman 292/353; 403/361; 403/383 [51] Int. Cl. Fl6d 1/06; F05b 3/00 57 ABSTRACT 1 [58] held of Search 35 3/ 2:Ids 3 3 A unitary molded control knob for an irregularly shaped rotatable shaft such as a D-shaft. The knob has a unitarily molded spring ramp element which receives [56] References the D-shaft flat and directs and biases the shaft tightly UNlTED STATES PA TENTS against an opposing shaft receiving wedge shaped wall 2,149,746 3/]939 Pfeiffcr 403/36l X as the shaft is slid axially into a shaft receiving cavity 1139-345 2/I940 Tcl&#39;fillm 403/333 bounded in part by the spring ramp and wedge shaped 2.670.227 &#39;l/l954 Green 403/36l X Wu 3.154.05l l0/l964 Durst ct all 74/531 UX 3.l88 l24 6/1965 Pestka et al. 403/383 4 Claims, 4 Drawmg Figures lg E MOLDED CONTROL KNOB FIELD OF THE INVENTION This invention relates to control knobs for rotary electrical controls and more particularly relates to knobs for irregularly shaped rotatable shafts such as D- shafts.  
 BACKGROUND AND SUMMARY OF THE INVENTION Electrical or other controls such as volume controls or switches which control various means in response to rotation of a control shaft have a rotatable manually manipulatable-control knob on the end of the shaft. Oftentimes it is desirable to readily removably mount the knob-on the end of the shaft while maintaining full rotational force fit between the knob and shaft. e.g.. when the knob-is disposed on one side of a control panel and the control means on the other side. with the shaft extending through the panel.  
  The knob preferably is-rernovable axially off of the end of the shaft. Heretofore. the knob&#39;was held on to the shaft by-a separate spring member. such as a metal leaf spring. which was mounted by other means in or around an aperture in the knob. The separate spring member also has been known to be molded in position within the knob by providing a special molded cavity which receives and positions the spring member prior to molding the knob thereabout. The present invention obviates these multiple parts and multiple molding steps by providing a unitary molded control knob which has a unitarily molded spring ramp element which yieldably receives the control shaft and holds the control shaft by spring biasing against an opposing wedge-shaped wall.  
  The present invention provides a unitary molded control knob which is capable of releasably receiving a shaft. The knob has a shaft receiver which includes a wall and an opposing guiding spring camming element. As the shaft is slid axially into the receiver. the camming element urges the shaft into tight engagement with a wedge-shaped wall portion of the receiver to hold the shaft.  
  Advantageously, the camming element may be a ramp member which engages the flat on a D-shaft during axial movement of the shaft. After the knob is mounted on the shaft, the engagement of the ramp with the shaft flat prevents rotational slippage between the knob and shaft and the spring biasing of the ramp against the opposite retainer wall holds the knob on the shaft. In a more specific form, the ramp is located on a somewhat resilientbridge member to provide more positive urging of the ramp against the flat.  
  While this invention is susceptible of embodiment in many different forms. there is shown in the drawings and will herein be described in detail a specific embodiment thereof, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a rear perspective view of a form of knob provided in accordance with this invention;  
  FIG. 3 is a vertical section through the knob of FIGS. 1 and 2 along line 3-3 of FIG. 4 and showing the knob mounted on the shaft of an electric control; and  
 FIG. 4 is a vertical section along line 4-4 of FIG. 3.  
 DESCRIPTION OF THE PREFERRED v EMBODIMENT Referring first to FIGS. 1 and 2. a unitary molded knob 10 has a face plate 12 and a molded cylindrical sidewall 14 which is joined to face plate 12 at a bevelled edge 15. An internal recess or cavity (FIGS. 1, 3 and 4) thereby is formed by face plate 12 and sidewall 14. Within the cavity is provided a cage structure. generally designated 16. molded integral with face plate 12 and having opposing open ends. The cage structure 16 is supported by radial strengthening ribs 18 which are also molded integral with face plate 12 and sidewall 14. as well as with cage 16.  
  Still referring to FIGS. 1, 3 and 4. the cage structure 16 includes a base or floor brace-like frame 20. side frames 22 upstanding from base frame 20 and joined to a wedge-shaped wall or roof structure 24. all of which define an interior shaft receiver 26 for receiving the round surface of a D-shaft 28 (FIGS. 3 and 4). In the form illustrated. the D-sahft 28 is the control shaft for a volume control in the form of a rheostat 30. but the knob can be used just as well on numerous other control devices. such as rotary switches or the like.  
  A unitarily molded bridge 32 is integral with base frame 20 and extends as a span from base frame 20 at the bottom of cage 16 beyond the front of cage 16. through an opening 34 in frame plate l2 under a gable 36 forming the front end of the roof structure 24. Bridge 32 then terminates in a hook shape at 38 having its reverse turned end merging and molded integral with face plate 12 at the bottom edge 34a of the opening 34. By extending the ramp through the opening 34. a greater length thereof is provided with greater resiliency therefor.  
  It will be seen that as D-shaft 28 is inserted axially into the rear of knob 10 (to the left in FIG. 3) and into the cage 16, the flat of the D-shaft rides up and over the top of ramp 40 as bridge 32 yields slightly. Ramp 40 supports and guides and shaft flat and urges the round of the shaft against the inside surface of the wedgeshaped roof structure 24. Finally once the D-shaft 28 is fully inserted the shaft end abuts the inside of a gable 36. D-shaft 28 will then rotate or turn with knob 10 and the slightly flatened upper edge of ramp 40 which supports the flat of the Dshaft prevents slippage between knob 10 and the D-shaft when the knob is turned.  
  The entire knob 10 is advantageously molded as a unitary or integral member as will be evident from its design with special reference to FIG. 3. The molding can take place in a single operation with the mold halves separating to the left and right as viewed in FIG. 3.  
 I claim:  
 1. A unitary knob for turning a D-shaft of an electrical control comprising a body having a front face and a cylindrical gripping portion. a receiver within said body having a floor portion which includes a resilient bridge spanning the receiver in the direction of shaft insertion, said bridge member extending from said receiver through said front face and having a hook shape with the reverse turned end of the hook shape formed integral with said face, a roof portion, and a rear opening for axially receiving the D-shaft and a stationary ramp element on said floor portion for receiving the flat portion of a D-shaft and directing the D-shaft during axial insertion into said receiver to press the cylindrical portion of the D-shaft against said roof portion and maintain the D-shaft in engagement with the roof portion whereby the shaft turns with the ramp preventing slipping.  
  2. A knob for turning a shaft comprising a unitary molded body which includes a front face and a receiver opening at the rear of the knob. said receiver having a floor. side frames extending from said floor for receiving the outer axial surface of a shaft. with a space adjacent said side frames from which the shaft may be moved radially against said side frames. a roof portion attached to said side frames. and cam means attached to a resilient bridge of said floor in said receiver for directing said shaft from said adjacent space into tight engagement with said roof portion as the shaft is moved axially into the receiver. said resilient bridge extending from said receiver and having a hook shape at the exterior of said receiver which joins with said front face of said knob.  
  3. A unitary molded knob for turning the D-shaft of a rotary electrical control comprising a face plate portion and a cylindrical sidewall portion joining said face plate portion and defining an open cavity within said knob. a central portion in said face plate portion. a cage structure in said cavity having opposite open ends. the first open end being in registry with said portion. rib means integral with said cage structure. face plate portion and cylindrical sidewall and supporting said cage structure portion within said cavity. said cage structure having a base frame portion and a pair of side frame portions upstanding therefrom and jointed to one end of a roof structure portion which has a gable at its other end above said port. a bridge member extending from said base frame portion through said port and having a hook shape at the exterior of said cavity turned back with the turned end of the hook shape joined to the front surface of said face plate portion at the base of said port. and a ramp element on said bridge member for receiving the flat of a D-shaft and camming the D- shaft during axial insertion into said cage through the second open end thereof to press the cylindrical portion of the D-shaft against the bottom of said roof structure before the end of the D-shaft moves into abutment with the inner surface of the gable. said bridge member being sufficiently resilient to maintain a bias on said ramp against the D-shaft flat and thereby maintain the D-shaft in tight engagement with the roof structure and interlock the knob with the D-shaft for rotary movement therewith.  
  4. A knob for turning a shaft comprised of a unitary molded body defining a front face and a receiver section which includes a ramp, a resilient bridge of a floor frame attached to said ramp, a roof section. side frames attaching said roof section to said floor frame. a gable attached to said roof section on said front face of said knob. ribs located within said knob for positioning said receiver section. said ramp prohibiting rotation of said shaft relative to said knob and urging said shaft against said roof section of said receiver. and said gable limiting axial movement of said shaft into said receiver.