Patent Publication Number: US-4481391-A

Title: Molded switch head

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to improvements in molded switch heads of the type shown in U.S. Pat. No. 2,820,123 issued to L. W. Higgins, R. S. Davis, and J. A. Herrmann. 
     Switches of the above noted type, in essence, provide first and second stationary contacts which are engaged and disengaged by a movable contact element or slug. The contact slug is positioned in the switch head and the switch head is further constructed so as to move an insulating barrier between the stationary contacts as the contact slug is moved to a disengaged position. The head is further constructed so as to completely surround the area of contact and engagement with an insulating means. Hence, as the switch head is moved to a disengaged contact position, arcing between the stationary contacts is decreased, first because of the interposition of the insulating barrier and secondly, because the amount of oxygen or ionizable gas present is restricted in view of the insulated enclosure around the contact area. 
     In the past, it has been the practice to attach an operating clamp to the top of the insulating material of the switch head. The operating clamp provides a means whereby the switch head is moved between the engaged and disengaged positions. The novel switch head disclosed in U.S. Pat. No. 2,820,123 comprises, in part, first and second insulating head sections which telescope together in a horizontal direction. These head sections are held together in an operating clamp which is formed of a spring steel material. It has been found that for short circuit currents of 10,000 amps or less, the head segments can be held together only by the clamp. However, in circuits having possible short circuit currents over 10,000 amps, it is necessary to cement the two head segments together to provide adequate protection when a short occurs. If the head sections are not cemented together in the presence of short circuit currents of over 10,000 amps, it is possible that the head segments will separate. 
     The present invention provides a solution to the expensive manufacturing step of cementing head segments together, as well as providing an alternative to the expensively formed spring operating clamp. 
     SUMMARY OF THE INVENTION 
     The present invention involves an improved switch head for engaging and making electrical contact between first and second stationary electrical conductors. The switch head comprises lower and upper insulating head sections, biasing means and a contact slug contained within the lower insulating head section for contacting and making electrical connection with the first and second stationary conductors, and clamping means for holding the lower and upper insulating head sections together. The clamping means places the lower and upper insulating head sections in compression when the switch head engages the first and second stationary conductors. The clamping means also applies a force to the lower head section to disengage the switch head from the first and second stationary conductors. 
     OBJECTS OF THE INVENTION 
     It is a general object of the present invention to provide an improved switch head for electrically connecting stationary electrical conductors. 
     It is a more specific object of the present invention to provide an improved switch head which is simple in design and inexpensive to manufacture. 
     It is another object to provide a switch head which is held together only by a clamp. 
     It is yet another object of the present invention to provide an improved switch head which is stronger in construction than prior art switch heads. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may thus be understood by reference to the following description, taken in conjunction with the accompanying drawings and the several figures of which like reference numerals identify like elements, and in which: 
     FIG. 1 is a side view of a novel switch head; 
     FIG. 2 is an exploded perspective view of the FIG. 1 switch head; 
     FIG. 2A is a side view of a clamp for use with the FIG. 2 switch head; 
     FIGS. 3, 4, and 5 are perspective views of parts of the FIG. 2 switch head; 
     FIGS. 6 and 7 are cross sectional views of parts of the FIG. 2 switch head; 
     FIG. 8 is a side view of an alternative embodiment of the novel switch head; 
     FIG. 9 is a perspective view of the FIG. 8 alternative embodiment; 
     FIG. 10 is an exploded perspective view of the FIGS. 8 and 9 alternative embodiment; and 
     FIGS. 11, 12, and 13 are cross sectional views of parts of the alternative embodiment of the novel switch head. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Whereas the invention may be implemented in various types of switch heads, it is preferably embodied in a switch of the nature shown in FIG. 1. FIG. 1 shows a side view of a novel improved switch head 20. A bar 22 moves the switch head 20 by means of a hanger 24 in a vertical direction (shown by the two headed arrow) to engage and disengage the switch head 20 from first and second stationary electrical conductors 26 and 28. The switch head 20 is shown in an exploded perspective view in FIG. 2. Electrical connection is established between the first stationary conductor 26 and the second stationary conductor 28 by contact slug 30 and biasing means 32. The contact slug 30 and the biasing means 32 are made of a metallic material, and the stationary conductors 26 and 28 are engaged between the slug 30 and the biasing means 32 as is disclosed and claimed in U.S. Pat. No. 2,820,123. 
     In a first embodiment, the novel switch head 20 comprises a body 34 having first and second ends 36 and 38. The first end 36 has a raised flange 40. The switch head also comprises a cap 42 having an outer wall 44 and a center portion 46 for mating with the raised flange 40 of the body 34. The center portion 46 of the cap 42 substantially contacts the biasing means 32 in the body 34 for retaining the biasing means 32 in position. The biasing means 32 and the slug 30 are contained within the body 34. 
     In general terms, the present invention involves an improved switch head for engaging and making electrical contact between the first and second stationary electrical conductors 26 and 28 and comprises lower and upper insulating head sections which are the body 34 and the cap 42, respectively. The improved switch head further comprises the biasing means 32 and the contact slug 30 contained within the lower insulating head section or body 34. The biasing means 32 and the slug 30 contact and make electrical connections with the first and second stationary conductors 26 and 28. The switch head also comprises a clamping means, such as a clamp 64, for holding the lower and upper insulating head sections 42 together. The clamping means places the lower and upper insulating head sections in compression when the switch head engages the first and second stationary conductors 26 and 28, and the clamping means applies force to the lower head section to disengage the switch head 20 from the first and second stationary conductors 26 and 28. The lower and upper insulating head sections are configured to mate in a vertical telescoping arrangement when the lower and upper insulating head sections are assembled. 
     FIGS. 3, 4, and 5 illustrate in more detail the body 34 and cap 42 of one embodiment of the present invention. The seciond end 38 of the body 34 has two rectangular openings 48 separated by a barrier 50 through which the first and second stationary conductors 26 and 28 pass as the switch head 20 engages the conductors 26 and 28. Within the body 34, slots 52 are used to position the contact slug 30, and posts 54 are utilized to position the biasing means 32. The outer wall 44 and center portion 46 of cap 42 are constructed such that they mate with the raised flange 40 of the body 34 in a vertical telescoping arrangement. FIGS. 6 and 7 are cross sectional views of the body 34 and cap 42, respectively, detailing the structure described above. 
     The body 34 and the cap 42 each have at least two oppositely opposed protruding abutments 56 and 58. The abutments 56 on the body 34 are aligned with the abutments 58 on the cap 42 when the body 34 and the cap 42 are assembled. The abutment 56 on the body 34 has a groove 60 on a lower end of the abutment 56, and the abutment 58 on the cap 42 has a recess 62 on an upper end of the abutment 58. (See FIGS. 6 and 7) 
     The clamping means comprises two identical clamps 64 as shown in FIG. 2A. The clamp 64 comprises a main portion 66 having first and second ends 68 and 69. The central opening 70 is provided in the main portion 66, and a finger 72 is attached to the first end 68 as shown in FIG. 2A. A pair of shoulders 74 is formed on the first end 68 of the main portion 66 and a hanger 24 is also attached to the first end 68. The hanger 24 may be configured in any one of a number of different ways, depending on the type of mechanism used to move the switch head. The cap 42 also has, near each abutment 58, a pair of walls 76, wherein each wall has a clamp engaging portion 78. The clamp engaging portion 78, in the present embodiment, comprises an overhanging section. 
     After the body 34 and cap 42 are assembled with the contact slug 30 and biasing means 32 contained within the body 34, the clamp 64 is attached and holds the switch head 20 together. The central opening 70 of the main portion 66 surrounds the abutments 56 and 58 on the body 34 and cap 42, respectively. The second end 69 of the main portion 66 engages the groove 60 in the lower end of the abutment 56 on the body 34, and the finger 72 attached to the first end 68 of the main portion 66 engages the recess 62 in the upper end of the abutment 58 on the cap 42. The pair of shoulders 74 on the first end 68 of the main portion 66 engages the clamp engaging portion 78 of the pair of walls 76 on the cap 42. It is understood that once the clamp 64 is positioned on the switch head 20, a force is applied to the finger 72 causing it to engage the recess 62 on the abutment 58. After this force has been applied to the finger 72, the clamp 64 is securely attached to the switch head 20 and prevents the body 34 from separating from the cap 42, even in the presence of severe arcing. The clamp 64 places the body 34 and the cap 42 in compression when the switch head engages the first and second stationary conductors 26 and 28; and furthermore, the clamp 64 applies force to the body 34 to disengage the switch head 20 from the first and second stationary conductors 26 and 28. 
     The body 34 and the cap 42 may be molded of any one of a number of well known insulating materials. The slug 30 is formed from a metallic material having good electrical conductors properties, and the biasing means 32 may be of spring steel formed in a stamping process. The clamp 64 may be stamped from metal, such as steel, and appropriately plated. 
     FIG. 8 shows a side view of an alternative embodiment of the present invention. A bar 22 operates on a hanger 80 to move the switch head 20 in a vertical direction to engage and disengage the switch head 20 from first and second stationary conductors 26 and 28. FIGS. 9 and 10 are perspective views showing the parts of the alternative embodiment. In the alternative embodiment pictured, a lower insulating head section or body 82 is provided having first and second ends 84 and 86. The first end 84 has an outer wall 88 and an inner wall 90 contained within the outer wall 88 such that the outer and inner walls 88 and 90 effectively form a continuous channel 92. A biasing means 94 and a contact slug 96 are contained within the body 82. The biasing means 94 and contact slug 96 contact and establish an electrical connection with the first and second stationary conductors 26 and 28 when the switch head 20 engages the conductors. 
     An upper insulating head section or cap 98 has a raised flange 100 for telescoping engagement with the channel 92 in the body 82. The raised flange 100 of the cap 98 substantially surrounds a center portion 102. The center portion substantially contacts the biasing means 94 in the body 82 for retaining the biasing means 94 in position. 
     The body 82 has protruding abutments comprising oppositely opposed pairs of ramp-like raised sections 104. A protruding abutment on the cap 98 comprises a substantially rectangular section 106 of predetermined height. 
     As shown in FIG. 9, a clamping means 108 is provided and comprises a main portion 110 with a substantially rectangular opening 112 for mating with the rectangular section 106 on the cap 98. First and second legs 114 are attached to and oppositely opposed on the main portion 110. Each of the legs 114 has a pair of tabs 116 for engaging the ramp-like raised sections 104 on the body 82. A hanger 80 is attached to the main portion 110 of the clamping means 108. The clamping means 108 places the body 82 and the cap 98 in compression when the switch head 20 engages the first and second stationary conductors 26 and 28; and furthermore, the clamping means 108 applies a force to the body 82 to disengage the switch head 20 from the first and second stationary contacts 26 and 28. 
     The invention is not limited to the particular details of the apparatus depicted and other modifications and applications are contemplated. Certain other changes may be made in the above described apparatus without departing from the true spirit and scope of the invention herein involved. It is intended, therefore, that the subject matter in the above depiction shall be interpreted as illustrative, not in a limiting sense.